Micromachined fluid handling apparatus with filter

ABSTRACT

The fluid handling devices are capable of accurately handling substantially continuous fluid flow rates as low as about 0.01 cc/day. The devices are so miniaturized, corrosion-resistant and non-toxic that they are suitable for being implanted in the human body; and are capable of being mass produced at costs so low, by using micromachining techniques, such as etching, that they may be considered to be disposable. The devices are either passive devices which consume no electrical energy at all, or are active devices which consume very small amounts of electrical energy. The devices are reliable because they may have as few as only two parts, only one which is a moving part; and because they may handle fluids at very low pressures. The fluid handling devices include active piezoelectrically driven membrane pumps; and passive fluid flow regulators, on-off valves, flow switches and filters.

This application is a division of prior application Ser. No. 08/131,762,filed on Oct. 4, 1993, abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to fluid handling devices. Moreparticularly, it relates to reliable, accurate, fluid handling deviceswhich are capable of handling fluid flow rates which are so low thatthey may be measured in hundredths of a cubic centimeter per day; whichmay have either a zero or an extremely small electrical energyconsumption; and which may be economically mass produced by usingmicromachining processes.

SUMMARY OF THE INVENTION

In many medical situations, it is desirable to continually administerfluid medication to a patient over an extended period of time at arelatively low flow rate. Examples of such cases are the use of morphinefor the treatment of malignant or non-malignant pain; the use of FUDRfor cancer chemotherapy; and the use of baclofen for the treatment ofintractable spasticity.

This manner of administering the medication is desirable because thelevel of the fluid medication in the patient's blood remains at arelatively constant, medically effective level. By way of contrast, ifthe medication was administered periodically in larger doses, such as intablet form by mouth, the level of the medication in the patient's bloodmay tend to fluctuate markedly over time, from too little to too much,rather than staying at the desired medically effective level.

Accordingly, one general aspect of the present invention may be toprovide fluid handling devices which are capable of continually handlingfluids over an extended period of time at relatively low flow rates,which may be as low as about 0.01 cc/day.

In many medical situations it is desirable to have fluid handlingdevices which are extremely small, so that they may be implanted withina patient's body. Accordingly, another general aspect of the presentinvention may be to provide fluid handling devices which are so smallthat they may be easily implanted within a patient's body.

However, when making a fluid handling device which is so small, itbecomes relatively easy to inadvertently clog any openings in the device(such as its ports, channels, cavities, or gaps) if a bonding materialis used to bond the various parts of the fluid handling device together.Accordingly, another general aspect of the present invention is toprovide fluid handling devices in which at least some of their parts areanodically bonded together, thereby eliminating the need to use aseparate bonding material to bond those parts together.

If the fluid handling devices are intended to be implanted in apatient's body, it is preferable that they either be passive devices,which do not consume any electrical energy at all; or, if they areactive devices, that they consume as little electrical energy aspossible for the quantity of fluid which they are to handle. This isimportant for at least two reasons. First, the less electrical energythe fluid handling devices consume, the smaller the batteries within theimplanted device may be, thereby enabling the implanted device to bemade smaller than might otherwise be the case. Second, the lesselectrical energy the fluid handling devices consume, the longer anyparticular size of battery will last; thereby avoiding frequent surgicalreplacement of the implanted device, or its batteries. Accordingly,another general aspect of the present invention may be to provide fluidhandling devices which, if they are passive devices, consume noelectrical energy at all; or, if they are active devices, consume aslittle electrical energy as possible for the quantity of fluid whichthey are to handle.

In medical situations, the reliability of the devices which handle thefluid medication must be very high. In general, reliability may beenhanced by simplifying the fluid handling devices to have as few totalparts as possible; to have as few moving parts as possible; and to havenominal operating pressures which are as low as possible. Accordingly,one general aspect of the present invention may be to provide fluidhandling devices which are inherently highly reliable because they mayhave a total of as few as two parts, as few as one of which may be amoving part. Another general aspect of the present invention may be toprovide fluid handling devices which may operate at pressures as low asabout 25 millimeters of mercury.

In medical situations, it is desirable to have fluid handling deviceswhich have a fail-safe design so that if they are subjected tooverpressures in excess of their nominal design limits, they are veryresistant to failure, so that they do not deliver excessive amounts ofthe medication to the patient. Accordingly, another general aspect ofthe present invention may be to provide fluid handling devices which,when subjected to an overpressure, may be resistant to being rupturedbecause their flexures or membranes may be at least partially supportedby at least one other element of the fluid handling devices; and whichmay reduce the flow of the medication, or shut it off altogether.

In view of the generally high cost of medical care, it is desirable toprovide high quality, accurate, reliable fluid handling devices at aprice which is so economical that the fluid handling devices may beconsidered to be disposable. Accordingly, another general aspect of thepresent invention may be to achieve these goals by using micromachiningprocesses to mass produce the fluid handling devices, or parts thereof.

Since many medications and body fluids are corrosive, particularly wherethe fluid handling device is used for an extended period of time, or isimplanted in a human or an animal, it is important that the fluidhandling device be corrosion-resistant. Accordingly, three furthergeneral aspects of the present invention may be to provide the fluidhandling device having a layer of one or more corrosion-resistantsubstances; to bond such a corrosion-resistant layer to the fluidhandling device by using anodic bonding; and to automatically performsuch anodic bonding of the corrosion-resistant layer at the time certainother parts of the fluid handling device are being anodically bondedtogether.

In many medical situations, it may be desirable to maintain the flowrate of the liquid medication to a patient at a predetermined rate,despite any fluctuations (either increases or decreases) in the pressureof the supply of the medication. For example, if the supply of themedication comprises a reservoir in which the medication is pressurizedwith a gas, as the reservoir is emptied the gas expands, therebyreducing the pressure on the decreasing amount of medication remainingin the reservoir. Accordingly, in addition to one or more of the abovegeneral aspects of the present invention, a specific aspect of thepresent invention may be to provide a fluid handling device in the formof a flow regulator which will maintain the flow of the medicationwithin predetermined parameters, despite fluctuations in the pressure ofthe medication which is received by the flow regulator, or fluctuationsin the pressure at the medication outlet port.

Such a flow regulator may comprise a substrate having fluid inlet means,a regulator seat, and fluid outlet means. The flow regulating device mayfurther comprise a flexure bonded to the substrate, and a regulator gapwhich is located between the flexure and the regulator seat.

During use, both the fluid inlet means and the outer surface of theflexure may be exposed to a source of liquid medication under pressure.The medication will flow sequentially through the fluid inlet means, theregulator gap and the fluid outlet means. As the medication flowsthrough the regulator gap, the height of the regulator gap will tend todecrease as the driving pressure difference across the regulatorincreases, and will tend to increase as the driving pressure differenceacross the regulator decreases. As a result, the regulator will tend tohold the flow rate of the medication constant, despite any fluctuationsin the driving pressure difference of the medication across the flowregulator.

Another specific aspect of the flow regulator of the present inventionmay be that its flow rate may be selectively increased or decreased byselectively increasing or decreasing the number, size, shape and lengthof its fluid inlet means.

A further specific aspect of the flow regulator of the present inventionmay be that its characteristic flow rate verses its applied drivingpressure difference response may be chosen by selectively adjusting thefluid flow resistances of the fluid inlet means and the regulator gapwith respect to each other.

Other specific aspects of the flow regulator of the present inventionmay be that it may be a radial flow regulator, in which at least aportion of its fluid inlet means extend at least substantially aroundits regulator seat's periphery; in which its flexure overlies itsregulator seat and extends outwardly past its regulator seat'speriphery; in which at least part of its fluid outlet means are locatedwithin its regulator seat; and in which the medication flows from itsfluid inlet means radially inwardly across its regulator seat's topsurface, from its regulator's periphery to its fluid outlet means.

Further specific aspects of the flow regulator of the present inventionmay be that it may be a linear flow regulator which may have anelongated regulator seat and an elongated flexure which extend betweenthe inlet means and the outlet means.

Other specific aspects of the linear flow regulator of the presentinvention may be that it may have a length to width ratio (L/W) in therange of from about 5:1 to about 1000:1, and preferably about 20:1; thatits flexure be unrestrained at its inlet means; and that its regulatorseat and flexure may follow a straight course, a non-straight course(such as circular, spiral, or sinuous), or a combination thereof.

Two further specific aspects of the linear flow regulator of the presentinvention may be that its regulator seat may have a contoured shape,such as the shape its flexure would assume if its flexure wasunsupported by its substrate, and was subjected to a certain drivingpressure difference across the regulator; and that such a contouredshape may be imparted to its regulator seat by pressure deflecting theflexure down into the substrate while the substrate is in a softenedstate, maintaining such pressure while the substrate is hardened, andthen releasing such pressure and permitting the flexure to return to itsoriginal, undeflected configuration.

Other aspects of the linear flow regulator of the present invention maybe that its regulator seat may comprise a channel in its substrate; thatits channel may not have a contoured shape; and that its channel may bemicromachined into its substrate by being etched into its substrate.

As was mentioned above, in many medical situations, it is desirable tobe able to administer a flow of fluid medication to a patient in an atleast substantially continuous manner over an extended period of time ata relatively low flow rate, in order to maintain a relatively constant,medically effective level of the medication in the patient's blood.

Accordingly, in addition to one or more of the above general aspects ofthe present invention, one specific aspect of the present invention maybe to provide a pump which is capable of producing such a flow of fluidmedication; wherein the pump may have a displacement per pumping cyclefrom about 0.05 microliters to about 10 microliters of medication (andpreferably about 1 microliters of medication); wherein the total flowrate of the pumping medication may be from about 0.01 cc/day to about20.00 cc/day (and preferably about 0.1 cc/day to 2.0 cc/day); andwherein the pumping cycle frequency may be as high as about 25 cyclesper second.

Another specific aspect of the pump of the present invention may be toprovide a pump which, for any given quantity of the pumped liquidmedication, utilizes as little electrical energy as possible, at drivingvoltages which are as low as possible. This goal may be achieved byproviding a pump having a pumping flexure which may be driven by apiezoelectric motor; wherein there may be an elastomeric joint betweenthe piezoelectric motor and the pumping flexure which reduces shearloads between the piezoelectric motor and the pumping flexure, therebydramatically increasing the energy efficiency of the pump by as much asfive times, and permitting driving voltages as low as about 50.0 voltsto be used. This goal may also be achieved by providing a pump having arelatively low operating pressure, in the range of from about 1.0 mm Hgto about 200 mm Hg, for example.

A further specific aspect of the pump of the present invention may be tohave its piezoelectric motor serve the dual functions of driving thepumping flexure, and protecting the pumping flexure from damage. Thisgoal may be achieved by selecting the piezoelectric motor to have adiameter larger than that of the pumping flexure; by bonding thepiezoelectric motor to the pumping flexure's outer surface; and bysizing the pump's substrate and the piezoelectric motor so that theperiphery of the piezoelectric motor is supported by the substrate. Inthis way, the piezoelectric motor may shield, and thus help prevent thepumping flexure from being damaged.

A still further specific aspect of the pump of the present invention maybe to protect its pumping flexure from damage which might otherwise becaused if the pumping flexure were driven into the pump's pumping cavitygreater than a predetermined amount. This goal may be achieved byproviding the pumping cavity with pumping flexure supports, which maysupport the pumping flexure, and which prevent the pumping flexure frombeing driven into the pump's pumping cavity greater than a predeterminedamount.

Another specific aspect of the pump of the present invention may be thatits internal features may be designed and arranged so that thepossibility of trapping bubbles within the pump are minimized; and sothat during operation of the pump, any bubbles within the pump may tendto be swept out of the pump by the flow of the medication through it.Such bubbles within the pump may be undesirable, since they mayinterfere with the proper operation of the pump's valves, and since theymay result the patient having a dangerous air embolism.

Further specific aspects of the pump of the present invention may bethat it minimizes, or even eliminates, any reverse flow of themedication through the pump, in the event the pump is subjected to anegative pressure difference; and any high forward flow of themedication through the pump, in the event the medication which issupplied to the pump is overpressurized, and exceeds a predeterminednominal value. This goal may be achieved by arranging the pump so thatwhen no voltage is supplied to the pump's piezoelectric motor, theweight and stiffness of the pumping flexure and the piezoelectric motormay tend to hold the pump's inlet valve closed. This goal may be furtherachieved by arranging the pump so that when a reversed polarity voltageis applied to the piezoelectric motor, the pumping flexure may be drivenagainst the inlet valve, to thereby hold the inlet valve closed. Thus,in the present invention the piezoelectric motor and the pumping flexuremay serve the dual functions of: (a) pumping the medication, and (b)minimizing, or even eliminating, reverse flows of the medication throughthe pump, and high forward flows of the medication through the pump inthe event of an overpressurization situation.

Another specific aspect of the pump of the present invention may be thatit may have a minimal amount of complexity and cost. This goal may beachieved by avoiding the deep etching of features into both faces of thepump's substrate; and by using, instead, the shallow etching of featuresinto only one face of the pump's substrate. This goal may also beachieved by the pump using passive inlet and outlet valves.

A further specific aspect of the pump of the present invention may bethat a residual amount of the medication is maintained in the pump'spumping cavity at all times during the pump's complete pumping cycle.This may permit the pump to be operated at a higher pumping cyclefrequency, and may also increase the energy efficiency of the pump,since the residual medication in the pumping cavity may provide a lowresistance path for the new medication which enters the pumping cavityduring each pumping cycle.

Other specific aspects of the pump of the present invention may be thatit may have integral inlet and outlet valves, whose valve seats areformed in the pump's substrate; wherein the inlet valve is whollycontained within the pump's pumping cavity; and wherein the outlet valveseat is wholly contained with the pump's outlet valve cavity. Inaddition, the pump may comprise as few as four basic components (namelya substrate, a one-way inlet valve, a membrane and a piezoelectricmotor); and wherein the membrane may serve the quadruple functions ofbeing the pump's pumping flexure, the outlet valve's flexure, the sealfor the pump's pumping cavity, and the seal for the pump's outlet valvecavity.

Further specific aspects of the pump of the present invention may bethat the pump's inlet valve may be located adjacent to an edge of thepump's pumping cavity; and wherein the pump's outlet valve may belocated either in the center of the pumping cavity, or as far from theinlet valve as possible. This may enable the pump to automatically primeitself very reproducibly during operation, due to the surface tensionbetween the medication and the pumping cavity's edge; and may enable thepump to avoid forming or trapping bubbles within the pumping cavity, byenabling the medication to sweep any bubbles out of the pumping cavityas the medication travels across the pumping cavity from the inlet valveto the outlet valve.

Other specific aspects of the pump of the present invention may be thatthe pump may be a modular pump. That is, the pump may comprise a pumpingportion module, an inlet valve module, and an outlet valve module;wherein the completed pump may be made by assembling these three modularcomponents together.

A further aspect of the modular pump of the present invention may bethat it may be arranged to have an outlet valve seat located within itspumping cavity. This arrangement may have several advantages. First,when no voltage is supplied to the pump, the weight and stiffness of thepumping flexure and the piezoelectric motor may tend to hold the pumpingflexure against the outlet valve seat; thereby minimizing, or eveneliminating, high forward flows of the medication through the pump inthe event of an overpressurization situation. Second, when a reversedpolarity voltage is applied to the piezoelectric motor, the pumpingflexure may be driven against the inlet valve, to thereby hold the inletvalve closed. Thus, here again, in the present invention thepiezoelectric motor and the pumping flexure may serve the dual purposesof: (a) pumping the medication, and (b) minimizing, or even eliminating,high forward flows of the medication through the pump in the event of anoverpressurization situation. Third, if the upper faces of thepiezoelectric motor/pumping flexure combination is exposed to themedication at the pump's inlet pressure, then the pump may functionallybehave as if it were a radial flow regulator; and may thereby reduce, oreven stop, the flow of the medication through the pump in the event ofan overpressurization situation.

Another specific aspect of the present invention may be that the maximumflow rate of the medication through the pump may be regulated byadjusting the size of the pump's inlet port, outlet port, and the heightof the gap between the pump's substrate and the modular inlet valve'sflexure.

In addition to one or more of the above general aspects of the presentinvention, one specific aspect of the present invention may be toprovide a micromachined one-way valve which will permit the medicationto flow through it in only one direction, with very low fluid flowresistance in the forward direction, and with very high fluid flowresistance in the reverse direction. The one-way valve may comprise asubstrate defining an inlet port, and an inlet valve seat. A membranemay be secured to the substrate and comprise at least one outlet port,and a flexure which extends over the inlet valve seat. During operation,as medication under a positive pressure is applied to the substrate'sinlet port, the medication flows in through the inlet port, lifts andunseats the membrane from the inlet valve seat, flows between theflexure and the inlet valve seat, and exits the one-way valve throughthe membrane's outlet port.

Another specific aspect of the one-way valve of the present inventionmay be that the inlet and outlet ports of the one-way valve may belocated on opposite sides of the one-way valve, to enable the one-wayvalve to be used as both an inlet one-way valve, and as an outletone-way valve, simply by turning the one-way valve over.

Other further specific aspects of the one-way valve of the presentinvention may be that the flexure may be elongated; that the flexure mayhave at least a portion of both of its ends anchored to the substrate;that the flexure's bottom surface and the inlet valve seat's top surfacemay be coplanar; and that the inlet valve seat may have any suitableshape, such as ring-shaped or rectangular.

A further specific aspect of the one-way valve of the present inventionmay be that the elongated flexure having anchored ends may not need tohave a rigid center boss for sealing between the flexure and the valve'sinlet valve seat. Such a flexure offers the advantage that it has aflexibility which is increased considerably as compared to theflexibility of a flexure which does have such a rigid center boss. Ithas also been discovered that such increased flexibility of the flexuremay be translated into either a smaller one-way valve, or a one-wayvalve which has a lower forward pressure drop.

Another specific aspect of the one-way valve of the present inventionmay be that the elongated flexure having anchored ends may beprestressed (i.e., stretched), across the inlet valve seat, so that at azero driving pressure difference across the one-way valve, the flexureis under a tension which may tend to hold it against the inlet valveseat, and prevent any flow of the medication across the inlet valveseat. Such prestressing of the flexure may offer numerous advantages.Among such advantages are that the one-way valve may have a greatresistance to permitting any medication to "bleed" from its outlet whenthe one-way valve is subjected to a supposedly zero driving pressuredifference (P) across the one-way valve; that the one-way valve may havea great resistance to permitting any medication to flow through it whenthe one-way valve is subjected to a negative driving pressure difference(P); that the one-way valve may offer a smoother change in its flow rate(Q) as a function of the driving pressure difference (P) across theone-way valve; that there may be a greater uniformity in the performanceof the one-way valve when it is mass produced; that the forward openingcharacteristics of the one-way valve may be tuned; and that the edges ofthe flexure may have less tendency to curl, which curling mightotherwise interfere with the proper operation of the one-way valve.

A further specific aspect of the one-way valve of the present inventionmay be that the elongated flexure having anchored ends may beprestressed by choosing the substrate and the flexure to be manufacturedfrom materials having different coefficients of thermal expansion;securing the substrate and the flexure together at a temperature whichis substantially different from the one-way valve's designed operatingtemperature range; and then returning the one-way valve to its designedoperating temperature range, so that the flexure is automaticallyprestressed due to the difference in the coefficients of thermalexpansion of the substrate and the flexure. In addition, the elevatedbonding temperature may also help to conform the mating surfaces of theinlet valve seat and the flexure with each other, to help prevent backflow leakage of the medication therebetween.

Other specific aspects of the one-way valve of the present invention maybe that the substrate may have etched into one of its faces aring-shaped inlet cavity having a central, projecting inlet valve seat;wherein the inlet valve seat's top surface may higher than the topsurface of the rest of the substrate; wherein the flexure may becircular, may have its periphery secured to the substrate, and may havea centrally located outlet port located over the inlet valve seat;wherein the outlet port may be smaller than the inlet valve seat; andwherein the flexure may be prestressed, due to the height differencebetween the top surfaces of the inlet valve seat and the rest of thesubstrate, which may tension the flexure by causing an interference fitbetween the inlet valve seat and the flexure. A one-way valve havingsuch a prestressed circular flexure offers most, if not all, of theadvantages set forth above regarding the one-way valve having anelongated flexure with anchored ends.

Another specific aspect of the one-way valve of the present inventionhaving a circular flexure may be that the membrane and the flexure maybe secured to the substrate despite the interference fit between theinlet valve seat and the flexure by forming the membrane and flexurefrom a wafer of material; by choosing the wafer to comprise a materialwhich may be relatively stiff at an elevated anodic bonding temperature;by choosing the substrate to comprise a material which may be relativelyelastic at the elevated anodic bonding temperature; by using anodicbonding at the elevated anodic bonding temperature to bond the wafer tothe substrate, wherein the relatively stiff wafer may compress therelatively elastic inlet valve seat and permit the wafer to beanodically bonded to the substrate; and by then reducing the wafer tothe final thickness of the membrane and the flexure, therebyautomatically freeing the inlet valve seat from its compressedconfiguration and permitting it to return to its original, uncompressedconfiguration. The elevated bonding temperature may also help to conformthe mating surfaces of the inlet valve seat and the flexure with eachother, to help prevent back flow leakage therebetween.

A further specific aspect of the one-way valve of the present inventionmay be that it may not need to have a separate stop for limiting thepredetermined maximum travel of the flexure away from the inlet valveseat. Such a predetermined maximum travel of the flexure would, in turn,limit the predetermined maximum flow rate (Q) of the medication throughthe one-way valve, for the predetermined maximum driving pressuredifference (P) across the one-way valve. This may be accomplished in atleast three ways. First, the flexure may be elongated, and may have bothof its ends secured to the substrate, so that, at a predeterminedmaximum driving pressure difference (P) across the one-way valve, theflexure may have a pre-determined maximum deflection as it bows awayfrom the inlet valve seat. Second, the flexure may be circular, theoutlet port may be located in the flexure, and the flexure may have itsouter periphery secured to the substrate, so that at a predeterminedmaximum driving pressure difference (P) across the one-way valve, theflexure may have a pre-determined maximum deflection as it balloons awayfrom the inlet valve seat. Third, the predetermined maximum deflectionof the flexure may be limited by a stop portion of whatever object towhich the one-way valve may be secured.

Another specific aspect of the one-way valve of the present inventionmay be that when it is mounted in its intended location of use on anobject, the flexure may be located in close proximity to a surface onthe object, and at least a portion of the medication which exits saidone-way valve may pass through a gap between said flexure and saidsurface on said object. As a result, said flexure, said gap, and saidsurface on said object may form a fluid flow regulator, to regulate theflow rate (Q) of the medication from said one-way valve, and to hold itwithin, or below, a predetermined range of values. That is, if thedriving pressure difference (P) decreases, then the flexure will tend tobe deflected towards said surface on said object a decreased amount,thereby increasing the height of the gap. This, in turn, tends tomaintain the flow rate (Q) at a relatively constant value, despite thereduced driving pressure difference (P). This is because the increasedheight of the gap will tend to compensate for the reduced drivingpressure difference (P) by increasing the flow rate (Q) which wouldotherwise occur at that reduced driving pressure difference (P). On theother hand, if the driving pressure difference (P) across the flexureincreases, then the flexure will tend to be deflected towards saidsurface on said object an increased amount, thereby reducing the heightof the gap. This, in turn, tends to maintain the flow rate (Q) at arelatively constant value, despite the increased driving pressuredifference (P). This is because the reduced height of the gap will tendto compensate for the increased driving pressure difference (P) byreducing the flow rate (Q) which would otherwise occur at that increaseddriving pressure difference (P). Lastly, at still higher drivingpressure differences (P) the flow rate (Q) is gradually reduced to zero,as the flexure is driven closer and closer to said surface on saidobject.

In many medical situations, it may be desirable to automatically switchoff the flow of the medication to a patient if the medication exceeds apredetermined pressure or flow rate, in order to prevent the patientfrom receiving an overdose of the medication; and to automaticallyswitch the flow of the medication back on, once the pressure of themedication falls below that predetermined pressure.

Accordingly, in addition to one or more of the above general aspects ofthe present invention, a specific aspect of the present invention may beto provide a fluid handling device in the form of a flow switch whichwill automatically switch off the flow of the medication through theflow switch in the event the medication exceeds a predetermined pressureor flow rate, and which will automatically switch the flow of themedication through the flow switch back on once the pressure of themedication falls below that predetermined pressure.

Such a flow switch may comprise a substrate having a inlet switch seat,and outlet means. The flow switch may further comprise a membranesecured to the substrate, wherein the membrane's mounting portion issecured to the substrate, the membrane's flexure extends partially overthe inlet switch seat, and the flexure's inlet port is located over theinlet switch seat. A switch gap is located between the flexure and theswitch seat.

During use, the flexure's top surface and the inlet port are exposed toa source of the medication under pressure. The medication will flowsequentially through the inlet port, radially outwardly across theswitch seat's top surface in the switch gap, and out through the outlet.As the driving pressure difference (P) of the medication across the flowswitch is increased from zero, the medication gradually forces theflexure closer to the switch seat, thereby gradually decreasing theheight of the switch gap (and vice versa).

Then, at a predetermined overpressure of the medication, i.e., at apredetermined driving pressure difference switch point (P_(SW)), theflexure automatically begins an irreversible collapse that results inthe flexure being forced by the medication against the inlet switchseat, and being held there by the medication, thereby automaticallyclosing the switch gap, switching off the flow switch, and stopping theflow of the medication through the flow switch.

Then, when the driving pressure difference (P) across the flow switch isdecreased to less than the predetermined overpressure, i.e., isdecreased to less than the driving pressure difference switch point(P_(SW)), the resiliency and elasticity of the flexure cause it toautomatically move away from the inlet switch seat, therebyautomatically opening the switch gap, switching the flow switch back on,and permitting the medication to flow through the flow switch onceagain.

In many medical applications the fluid flow rates of the medication maybe very low, such as from about 0.01 cc per day to about 10.00 cc perday. As a result, the fluid passages in the fluid handling devices whichare capable of dealing with such very low flow rates have dimensionswhich may be as small as one or two microns, or less. Thus, thepotential exists for such very small fluid passages to be clogged byeven very small particles in the medication.

Accordingly, in addition to one or more of the above general aspects ofthe present invention, a specific aspect of the present invention may beto provide a fluid handling device in the form of a filter which willfilter out from the medication particles which may have a size as smallas about 0.02 micron, or less.

A further specific aspect of the filter of the present invention may beto provide a filter comprising as few as two basic components, namely asubstrate and a membrane.

Another specific aspect of the filter of the present invention may bethat the filter may share its substrate and membrane with at least oneother fluid handling device, wherein such other fluid handling devicealso comprises the same substrate and membrane, and may receive filteredmedication from the filter through fluid passages defined between thesame substrate and membrane.

Further specific aspects of the filter of the present invention may beto provide a radial array filter having a ring-shaped radial array offilter slots which are manufactured in the substrate; wherein themembrane serves as the cover for the filter slots; and wherein anotherfluid handling device, which is to receive the filtered medication fromthe radial array filter, is located concentrically within thering-shaped radial array of filter slots.

Another specific aspect of the radial array filter of the presentinvention may be that it further comprises a ring-shaped inlet cavity,for distributing the incoming medication substantially equally to all ofthe filter slots; and a ring-shaped outlet cavity, for collecting thefiltered medication from the filter slots substantially equally. Theinlet and outlet cavities may also serve to provide a relatively uniformpressure drop across all of the filter slots.

A further specific aspect of the present invention may be to provide aslab filter comprising a filter element suspended over an outlet cavityin the substrate; and an inlet port in the membrane for permitting themedication to reach the filter element.

Other specific aspects of the present invention may be to provide a slabfilter in which the edges of the filter element may sandwiched betweenthe substrate and the membrane; and which may have a filter elemententrance through which the filter element may be inserted into placeover the slab filter's outlet cavity.

Although all of the forgoing comments regarding the fluid handlingdevices of the present invention have been with reference to handlingmedicinal fluids in a medical context, it is understood that the fluidhandling devices of the present invention may also be used to handle anytype of non-medicinal fluid, in both medical and non-medical contexts.In addition, although the fluid handling devices which were mentionedabove may be very small and may handle fluids at very low flow rates andat relatively low pressures, it is understood that, by applying scalinglaws, the fluid handling devices of the present invention may, ingeneral, be scaled up to any desired size; to handle any desired fluidflow rate and pressure. Further, the term "fluid" is used in its broadsense, and includes both liquids and gasses.

It should be understood that the foregoing summary of the presentinvention does not set forth all of its features, advantages,characteristics, structures, methods and/or processes; since these andfurther features, advantages, characteristics, structures, methodsand/or processes of the present invention will be directly or inherentlydisclosed to those skilled in the art to which it pertains by thefollowing, more detailed description of the present invention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a top elevational view of a micromachined radial flowregulator of the present invention;

FIG. 2 is a cross-sectional view thereof, taken substantially along line2--2 of FIG. 1;

FIG. 3 is a graph depicting certain of the fluid flow characteristicsthereof;

FIG. 4 is a schematic diagram of some of the fluid characteristicsthereof;

FIGS. 5 and 6 are graphs depicting certain further fluid flowcharacteristics thereof;

FIG. 7 is a perspective view, partly in a cross-section takensubstantially along line 7--7 of FIG. 8, of a micromachined linear flowregulator of the present invention having a contoured regulator seat;

FIG. 8 is a top elevational view thereof;

FIGS. 9-11 are top elevational views of three additional embodimentsthereof;

FIG. 12 is a graph depicting certain fluid flow characteristics thereof;

FIG. 13 is a perspective view, partly in a cross-section takensubstantially along line 13--13 of FIG. 14, of a micromachined linearflow regulator of the present invention having a non-contoured regulatorseat;

FIG. 14 is a top elevational view thereof;

FIG. 15 is a is a graph depicting certain fluid flow characteristicsthereof;

FIG. 16 is a perspective view, partly in a cross-section takensubstantially along line 16--16 of FIG. 17, with certain parts brokenaway, of a micromachined diaphragm pump of the present invention havingintegral valving and a centrally located inlet port;

FIG. 17 is a top elevational view of the entire substrate thereof;

FIG. 18 is a perspective view, partly in a cross-section takensubstantially along line 18--18 of FIG. 19, with certain parts brokenaway, of a micromachined diaphragm pump of the present invention havingintegral valving and an edge located inlet port;

FIG. 19 is a top elevational view of the entire substrate thereof;

FIG. 20 is a cross-sectional view, partly in a cross-section takensubstantially along line 20--20 of FIGS. 21-22, of a micromachineddiaphragm pump of the present invention having modular valving and anedge located inlet port;

FIG. 20A is a fragmentary cross-sectional view of a modification of theinlet portion thereof;

FIG. 21 is a top plan view of the entire substrate thereof;

FIG. 22 is bottom plan view of the pump of FIG. 20;

FIG. 23 is top plan view of a first embodiment of the micromachinedone-way valve of the present invention;

FIG. 24 is a cross-sectional view thereof, taken substantially alongline 24--24 of FIG. 23;

FIG. 25 is a cross-sectional view thereof, taken substantially alongline 25--25 of FIG. 23;

FIG. 26 is top plan view of a second embodiment of the micromachinedone-way valve of the present invention;

FIG. 27 is a cross-sectional view thereof, taken substantially alongline 27--27 of FIG. 26;

FIG. 28 is a cross-sectional view thereof, taken substantially alongline 28--28 of FIG. 26;

FIG. 29A is a graph depicting certain fluid flow characteristics of thefirst embodiment of the micromachined one-way valve of the presentinvention;

FIG. 29B is a graph depicting certain fluid flow characteristics of thesecond embodiment of the micromachined one-way valve of the presentinvention;

FIG. 29C is a schematic representation of certain factors used in amathematical model thereof;

FIG. 30 is a top plan view of a third embodiment of the micromachinedone-way valve of the present invention;

FIG. 31 is a cross-sectional view thereof, taken substantially alongline 31--31 of FIG. 30;

FIG. 32 is a graph depicting certain fluid flow characteristics thereof;

FIG. 33 is a cross-sectional view of the micromachined membrane flowswitch 250 of the present invention, taken substantially along line33--33 of FIG. 34;

FIG. 34 is a top elevational view thereof;

FIGS. 35-38 are graphs depicting certain fluid flow characteristicsthereof;

FIG. 39 is a top elevational view of the substrate of the micromachinedradial array filter of the present invention;

FIG. 40 is a cross-sectional view thereof, taken substantially alongline 40--40 of FIG. 39;

FIG. 41 is a top elevational view of the substrate of a first embodimentof the micromachined slab filter of the present invention;

FIG. 42 is a cross-sectional view thereof, taken substantially alongline 42--42 of FIG. 41;

FIG. 43 is a cross-sectional view thereof, taken substantially alongline 43--43 of FIG. 41; and

FIG. 44 is a top elevational view of the substrate of a secondembodiment of the micromachined slab filter of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS MICROMACHINED RADIAL FLOWREGULATOR 32 (FIGS. 1-6): STRUCTURE

Turning now to FIGS. 1-2, the micromachined radial flow regulator 32 ofthe present invention may be used to control the flow rate of a fluidmedication 12 passing through it. The term "medication" is used in itsbroad sense throughout this document, and may be any fluid, whether ornot the fluid is medicinal in nature; unless the context should indicateotherwise. Similarly, the term "fluid" is also used in its broad sensethroughout this document, and may include both liquids and gasses;unless the context should indicate otherwise.

The radial flow regulator 32 may comprise a substrate 34 and a membrane36. The substrate 34 may have four radially oriented inlet channels 38,a ring-shaped inlet cavity 40, a ring-shaped regulator seat 42 acylindrical outlet cavity 52 and a venturi-shaped outlet port 54. InFIG. 1, the membrane 36 is depicted as being transparent, for clarity,so that the substrate 34's various features may be seen more easily.

The membrane 36 may have four mounting portions 26, which are mounted torespective portions of the substrate 34's top surface 46; a circular,flexible flexure 28, which lies over the inlet cavity 40 and theregulator seat 42; and four inlet channel cover portions 30, each ofwhich lie over a respective inlet channel 38. Although the membrane 36is illustrated as being of uniform thickness, and as having flat bottomand top surfaces 50, 62, the membrane 36 may not be of uniformthickness, and may have bottom and top surfaces 50, 62 which are notflat. Although the membrane 36 is illustrated as having four mountingportions 26, it may have fewer or more mounting portions 26.

A ring-shaped regulator gap 48 is provided between the regulator seat 42and the flexure 28.

Although four, straight, radially oriented inlet channels 38 areillustrated, each having a rectangular cross-sectional configuration anda respective cover portion 30, there may be fewer or more inlet channels38, each having a respective cover portion 30; any particular inletchannel 38 may have any other suitable size and cross-sectionalconfiguration, such as square or rounded; the length of any particularinlet channel 38 may be varied; and any particular radial inlet channel38 need not follow a straight, radially oriented course, but may followa circular, spiral, serpentine, or other non-straight, non-radiallyoriented course, such as do the channels 86 of the regulators 80 ofFIGS. 9-11. The use of one or more inlet channels 38 following acircular, spiral, serpentine, or other non-straight, non-radiallyoriented course may be desirable since it may permit the manufacture ofa radial flow regulator 32 which is more compact, as compared to aradial flow regulator 32 having straight, radially oriented inletchannels 38.

Although the ring-shaped inlet cavity 40 is illustrated as having acircular or cylindrical configuration, and a uniform depth, it may haveany other suitable size and configuration, and a non-uniform depth. Inaddition, although the inlet channels 38 and the inlet cavity 40 areillustrated as being separate elements, it is understood that theseelements may be merged into each other so that they are no longerdistinct elements. This may be done in any suitable way, such as byenlarging the inlet channels 38 until they perform most, if not all, ofthe functions of the inlet cavity 40; by enlarging the inlet cavity 40until it performs most, if not all, of the functions of the inletchannels 38; or by any combination of the forgoing two ways.

Although the ring-shaped regulator seat 42 is illustrated as having acircular or cylindrical configuration, a flat top surface 44, and auniform thickness, it may have any other suitable size andconfiguration, a top surface 44 which is not flat, and a non-uniformthickness.

Although the ring-shaped regulator gap 48 is illustrated as having acircular or cylindrical configuration, and a uniform height, it may haveany other suitable size and configuration, and a non-uniform height.Although the regulator gap 48 is illustrated as being formed byselecting the regulator seat 42 to have a thickness such that its topsurface 44 is lower than the portions of the substrate 34's top surface46 to which the membrane 36's mounting portions 26 are secured, theregulator gap 48 may be formed in any other suitable way. For example,the regulator seat 42's top surface 44 and the substrate 34's topsurface 46 may be selected to be co-planar, and the regulator gap 48 maybe formed by reducing the thickness of the portion of the flexure 28which overlies the regulator 42 by an amount equal to the desired heightof the regulator gap 48. Alternatively, the regulator gap 48 may beformed by a combination of the two forgoing ways.

Although a single outlet cavity 52, and a single outlet port 54 areillustrated, there may be more than one of each of these elements.

Although an outlet cavity 52 having a circular or cylindricalconfiguration and a uniform depth is illustrated, it may have any othersuitable size and configuration, and a non-uniform depth. The outletcavity 52 may be used to define a clean outer perimeter for the outletport 54, particularly if the outlet port 54 is drilled with a laser.However, the outlet cavity 52 may be eliminated, and the outlet port 54may be extended upwardly so that it communicates directly with theregulator gap 48. Alternatively, the outlet port 54 may be eliminated,and the outlet cavity 52 may be extended downwardly so that itcommunicates directly with the regulator 32's bottom surface 56.

Although an outlet port 54 having a venturi-shaped configuration isillustrated, it may have any other suitable configuration, such as roundor cylindrical.

Although the inlet cavity 40, the regulator seat 42, the regulator gap48, the outlet cavity 52 and the outlet port 54 are illustrated as beinguniformly arranged with respect to each other around a common center,they may be arranged with respect to each other in any other suitableway, and may not have a common center.

The regulator 32 may have a flow rate for medical applications in therange of from about 0.01 cc/day to about 20 cc/day; and preferably inthe range of from about 0.1 cc/day to about 2.0 cc/day. However, it isunderstood that, in view of all of the disclosures contained in thisdocument, the radial flow regulator 32 may be scaled up or down in sizeto regulate higher or lower flow rates of the medication 12.

By way of example, the chip bearing the radial flow regulator 32 may bea square having sides about 4.83 mm long. Its membrane 36 may bemanufactured from silicon; and may have a thickness of about 25 microns.Its substrate 34 may have a thickness of about 0.5 mm, and may bemanufactured from 7740 Pyrex glass, manufactured by the Corning Companylocated in Corning New York. The inlet channels 38 may have a length ofabout 2.54 mm, a width of about 107 microns, and a depth of about 5.65microns. The ring-shaped inlet cavity 40 may have a depth of about 5.65microns, an O.D. (outer diameter) of about 2.29 mm, and an I.D. (innerdiameter) of about 1.52 mm, (i.e., the ring-shaped cavity 40 may have aradial width of about 0.77 mm). The ring-shaped regulator seat 42 mayhave an O.D. of about 1.52 mm and an I.D. of about 0.5 mm, (i.e. thering-shaped regulator seat 42 may have a radial width of about 1.02 mm).The ring-shaped regulator gap 48 may have a height of about 2.5 microns,when the driving pressure difference (P) across the flexure 28 is zero;and may have a radial width of about 1.02 mm. The outlet cavity 52 havea width of 0.5 mm, and a depth of about 3.15 microns. The outlet port 54may have a minimum diameter of about 100 microns, and a depth of about494 microns. The flow characteristics of this example radial flowregulator 32 are illustrated in FIGS. 5 and 6.

As will be appreciated from all of the disclosures in this document, thefact that the regulator 32 may, as in the example set forth above, havean extremely small size, be extremely light weight, have only two parts,and have a zero electrical energy consumption, offer numerous advantagesover a regulator 32 which was physically much larger, much heavier, morecomplex or consumed electrical energy. For example, the regulator 32 maybe ideal for use as part of a miniaturized medication delivery devicewhich is to be implanted in a human or animal for delivery of constantflows of the medication 12 at flow rates as low as about 0.01cc/day--flow rates which are so low that they may be impossible for aphysically larger flow regulator of a different design to reliably andaccurately deliver.

MICROMACHINED RADIAL FLOW REGULATOR 32 (FIGS. 1-6): OPERATION AND DESIGN

The radial flow regulator 32 may be installed in its intended locationof use in any suitable way. Any suitable medication supply means may beused to connect the radial flow regulator 32's inlet channels 38 to asource of the medication 12; and any suitable medication delivery meansmay be used to connect the radial flow regulator 32's outlet port 54 towhatever person, animal or thing is to receive the medication 12 fromthe outlet port 54. In some cases, the medication supply means may alsobe used to supply the medication 12 to the flexure 28's top surface 62,at a pressure which may or may not be the same as the pressure at whichthe medication 12 is supplied to the inlet channels 38.

For example, the radial flow regulator 32 may be installed within anytype of reservoir means for the medication 12 by any suitable means,such as by locating the radial flow regulator 32's outlet port 54 overthe reservoir means's outlet, and by using an adhesive face seal betweenthe radial flow regulator 32's bottom surface 56 and the inside of thereservoir means to hold the radial flow regulator 32 in place. As aresult, when the reservoir means is filled with the medication 12, theradial flow regulator 32 will be immersed in the medication 12, with itsinlet channels 38 and its flexure 28's top surface 62 in fluidcommunication with the medication 12 within the reservoir means, andwith its outlet port 54 in fluid communication with the reservoir means'outlet. Such an installation for the radial flow regulator 32 hasnumerous advantages.

For example, it is quick, easy, reliable and inexpensive, because noadditional medication supply means (such as supply conduits) are neededto supply the medication 12 to the radial flow regulator 32's inletchannels 38 and to the flexure 28's top surface 62 (since they arealready immersed in the medication 12); and because no additionalmedication delivery means (such as delivery conduits) are needed toconvey the medication 12 away from radial flow regulator 32's outletport 54 (since the reservoir means' outlet is used for this purpose).Such additional inlet and outlet conduits may be undesirable since itmay be relatively time consuming, difficult and expensive to align andconnect them to radial flow regulator 32, due to the extremely smallsize of its inlet channels 38, flexure 28, and outlet port 54. Suchadditional inlet conduits may also be undesirable because they may tendto trap a bubble when being filled with a liquid medication 12, whichbubble might then be carried into the radial flow regulator 32 and causeit to malfunction.

In the discussion which follows it will be assumed, for clarity andsimplicity, that during operation of the radial flow regulator 32, theflexure 28's top surface 62 and the entrances of the inlet channels 38are all exposed to a pressurized source of the medication 12 from themedication supply means. It will also be assumed, for clarity andsimplicity, that the driving pressure difference (P) of the medication12 across the radial flow regulator 32 is the pressure differencebetween the medication 12 at the membrane 36's top surface 62, and themedication 12 at the outlet port 54; which is the same as the pressuredifference between the medication 12 at the entrances of the inletchannels 38 and the outlet port 54. However, it is understood thatduring operation of the radial flow regulator 23, these pressuredifferences need not be equal, and the flexure 28's top surface 62 doesnot necessarily have to be exposed to the pressurized source of themedication 12 from the medication supply means.

When the flexure 28's top surface 62 is exposed to the medication 12,the driving pressure difference (P) across the flexure 28 may be thedominant factor in determining the amount of deflection of the flexure28, and thus, the size of the regulator gap 48. On the other hand, ifthe flexure 28's top surface 62 is not exposed to the medication 12,then the velocity of the medication 12 through the regulator gap 48 maybe the dominant factor in determining the amount of the deflection ofthe flexure 28, and thus, the size of the regulator gap 48.

During operation, as a driving pressure difference (P) is applied acrossthe radial flow regulator 32, such as by pressurizing the source of themedication 12 with respect to the radial flow regulator 32's outlet port54 by any suitable means, the medication 12 will pass sequentiallythrough the radial flow regulator 32's inlet channels 38, inlet cavity40, regulator gap 48, outlet cavity 52, and outlet port 54. The inletcavity 40 may serve to more or less equally distribute the flow of themedication 12 from the inlet channels 38 to the entire circumference ofthe regulator gap 48, for more predictable operation of the radial flowregulator 32.

Referring now to FIG. 3, the regulator curves 64, 66, 68 and 70 areillustrated for a radial flow regulator 32 having one, two, three andfour radial inlet channels 38, respectively. The triangular, diamond,circular and square data points on the regulator curves 64, 66, 68 and70 are for the measured flow rate (Q) of an actual radial flow regulator32 having the physical parameters of the example radial flow regulator32 which was set forth above.

The regulator curves 64, 66, 68 and 70, as well as all of the datapoints in FIG. 3, are plots of the flow rate (Q) of the medication 12through the radial flow regulator 32 in microliters per day (μL/day), asa function of the driving pressure difference (P) across the radial flowregulator 32 in millimeters of mercury (mm Hg).

As seen in FIG. 3, at a zero driving pressure difference (p) there is noflow of the medication 12 through the radial flow regulator 32,regardless of how many inlet channels 38 there may be. Then, as thedriving pressure difference (P) is increased from zero, the radial flowregulator 32 exhibits four flow regimes, again regardless of the numberof inlet channels 38 which it may have.

That is, as the driving pressure difference (P) is increased from zero,there is a corresponding increase of the flow rate (Q); but there isalso a gradual lessening of the flow rate's (Q's) sensitivity to thedriving pressure difference (P). For example, this is seen on the curve66 from about a 0 mm Hg to about a 200 mm Hg driving pressure difference(P).

At intermediate driving pressure differences (P) there is a "controlzone" wherein the flow rate (Q) is relatively insensitive changes in thedriving pressure difference (P). For example, this is seen on the curve66 from mm Hg to about 300 mm Hg.

Then, at driving pressure differences (P) higher than the "controlzone", the flow rate (Q) actually decreases as the driving pressuredifference (P) increases. For example, this is seen on the curve 66 fromabout 300 mm Hg to about 450 mm Hg.

Finally, at very high driving pressure differences (P), not illustratedin FIG. 3, the flow rate (Q) may gradually decrease to near zero as thedriving pressure difference (P) of the medication 12 acting on theflexure 28's top surface 46 drives the flexure 28 down against theregulator seat 42.

It has been discovered that the radial flow regulator 32 has a built-in,fail-safe characteristic, due to its structure, that may provide theuser with exceptional protection against catastrophic failure of theflexure 28, when the flexure 28 is subjected to driving pressuredifferences (P) that are far in excess of the regulator 32's designeddriving pressure difference (P) range.

This fail-safe characteristic exists because, as has been mentioned, atvery high driving pressure differences (P) the medication 12 acting onthe flexure 28's top surface 46 may drive the flexure 28 down againstthe regulator seat 42's top surface 44. When this happens, the regulatorseat 42 then acts as a support for the flexure 28 and prevents itsfurther downward deflection; which further deflection might otherwisecause the flexure 28 to crack or rupture. As a result, a much higherdriving pressure difference (P) is required to rupture the flexure 28than would otherwise be the case, since the largest unsupported span ofthe flexure 28 is reduced in size from the maximum overall diameter ofthe inlet cavity 40, to the much smaller radial width of the ring-shapedinlet cavity 40. For example, for a flexure 28 which was a membrane ofsilicon about 25 microns thick, a driving pressure difference of atleast about 100 psi (5,171 mm Hg) would be required to crack or rupturethe flexure 28. By way of comparison, as seen in FIG. 3, the regulator32's typical operating driving pressure difference (P) may be only about300 mm Hg. Thus, in this instance, the regulator 32 would have about a17 times overpressure safety factor.

The type of response curves 64, 66, 68, 70 shown in FIG. 3 is highlydesirable for many applications. This is because the radial flowregulator 32 will deliver a relatively constant flow rate (Q) of themedication 12 in its nominal "control zone", despite a substantial rangeof variations in the driving pressure difference (P). In addition, ifthe nominal "control zone" driving pressure difference (P) is exceeded,then the flow rate (Q) of the medication 12 will not increase, but willactually decrease; thereby avoiding the possibility of damage whichmight otherwise be caused if the flow regulator 32 permitted more thanthe desired amount of the medication 12 to flow.

For example, let us assume that a medication delivery device, having asource of medication 12 under pressure, was equipped with a radial flowregulator 32 in order to control the flow rate (Q) of the medication 12from the medication delivery device. As a result, such a medicationdelivery device may be designed for operation in the radial flowregulator 32's above nominal "control zone" where the flow rate (Q) isrelatively insensitive to changes in the driving pressure difference(P). This may be highly desirable, since the patient will receive themedication 12 at the needed flow rate (Q); despite any variations in thedriving pressure difference (P), such as may be caused by the gradualemptying of the medication delivery device. In addition, if the nominal"control zone" driving pressure difference (P) were to be substantiallyexceeded, such as if a medical person accidentally overfilled themedication delivery device, then the medication flow rate (Q) willactually fall, thereby significantly reducing the possibility of injuryor death to the patient, due to an overdose of medication 12, whichmight otherwise occur.

The radial flow regulator 32 tends to maintain the flow rate (Q) of themedication 12 at a relatively constant value in its "control zone",despite changes in the driving pressure difference (P), in the followingway. If the driving pressure difference (P) increases, then the flexure28 will tend to be deflected downwardly towards the regulator seat 42 anincreased amount, thereby reducing the height of the regulator gap 48.This, in turn, tends to maintain the flow rate (Q) at a relativelyconstant value, despite the increased driving pressure difference (P).This is because the reduced height of the regulator gap 48 will tend tocompensate for the increased driving pressure difference (P) by reducingthe flow rate (Q) which would otherwise occur at that increased drivingpressure difference (P).

On the other hand, if the driving pressure difference (P) decreases,then the flexure 28 will tend to be deflected downwardly towards theregulator seat 42 a decreased amount, thereby increasing the height ofthe regulator gap 48. This, in turn, tends to maintain the flow rate (Q)at a relatively constant value, despite the reduced driving pressuredifference (P). This is because the increased height of the regulatorgap 48 will tend to compensate for the reduced driving pressuredifference (P) by increasing the flow rate (Q) which would otherwiseoccur at that reduced driving pressure difference (P).

Lastly, at driving pressure differences (P) above the regulator 32's"control zone" the flow rate (Q) is gradually reduced to near zero, asthe flexure 28 is driven down closer and closer to the regulator seat42.

Although the radial flow regulator 32 is deceptively simple inappearance, it has been discovered that it is not possible to developsimple, generally applicable design rules for its construction. This isin large part attributable to the close and nonlinear compensatorycoupling between the flow rate (Q) through the radial flow regulator32's regulator gap 48 and the flow resistance of the regulator gap 48(R,); which, in turn, makes it difficult to separate cause and effect ina mathematical sense.

In addition, certain other problems arise in developing simple,generally applicable design rules for the radial flow regulator 32because the flow rates (Q) of the medication 12 through the regulator 32may be so low, (as low as about 0.01 cc per day), and because thedimensions of the inlet channels 38, the inlet cavity 40, the regulatorgap 48, the outlet cavity 52 and the outlet port 54 may be so small, (assmall as about 0.1 microns).

As a result of such low flow rates (Q) and such small dimensions,certain fluid flow effects (such as the viscous shear forces of themedication 12 acting to deform various parts of the radial flowregulator 36), which are normally negligible in predicting theperformance of physically larger flow regulators, which handle flowrates of over about 0.1 cc per minute, for example, may become veryimportant. In addition, certain other fluid flow effects (such as theEquation of Continuity and Bernoulli's Equation), which are normallyimportant for physically larger flow regulators, handling such higherflow rates (Q), may become negligible for a regulator 32 having such lowflow rates (Q) and such small dimensions. And, at intermediate flowrates (Q) and dimensions, a combination of the pertinent small scale andlarge scale fluid flow effects may have to be taken into account.

Because of all of the above problems, it has been discovered that twoquite different strategies may be used to assist in designing a radialflow regulator 32 which has any particular desired flow regulationcharacteristics.

The first strategy is one which is empirical in nature. That is, aseries of flow regulators 32 may be built, and one feature at a time maybe varied, so that the effects of changing that particular feature maybe determined.

For example, the series flow resistance (R_(s)) of the regulator gap 48may be independently varied by holding constant the regulator gap 48'sinitial height (when the driving pressure difference (P) is equal tozero); while varying the width of the ring-shaped regulator seat 42,such as by varying the I.D. and O.D. of the ring-shaped regulator seat42. Similarly, the regulator gap 48's initial height (when the drivingpressure difference (P) is equal to zero) may be varied; while holdingconstant the width of the ring shaped regulator seat 42, such as byholding constant the I.D. and O.D. of the ring-shaped regulator seat 42.

By building and testing a large number of radial flow regulators 32; bythen plotting data points for each of them for their various flow rates(Q) versus their driving pressure differences (P); and by thencurve-fitting the plotted data points, it has been discovered that it ispossible to generate an empirical model for the performance of theradial flow regulator 32 which shows the relationships between keyfeatures of the radial flow regulator 32 and the operating behavior ofthe radial flow regulator 32. These empirical relationships may then beused to interpolate or extrapolate from known design cases to predictthe behavior of a new radial flow regulator 32.

For example, it has been discovered that the radial flow regulator 32'sflow rate set point (Q_(set)) (the average flow rate (Q) of the radialflow regulator 32 over its "control zone") obeys power-law relationshipswith respect to many of the radial flow regulator 32's design features.That is, it has been discovered that if the series flow resistance(R_(s)) of the regulator gap 48, and the regulator gap 48's initialheight (when the driving pressure difference (P) is equal to zero), areindependently varied, then the radial flow regulator 32's flow rate setpoint (Q_(set)) may be described over a considerable range of values byan equation of the form: ##EQU1## where (Q_(set)) and (R_(s)) are ashave been defined above; where (G) is the regulator gap 48's initialheight (when the driving pressure difference (P) is equal to zero); andwhere (a) is a constant.

For example, for a radial flow regulator 32 having a silicon flexure 28with a thickness of about 25 microns; having channels 38 with a width ofabout 107 microns, with a depth of about 5.65 microns, and a length ofabout 2.54 mm; having a ring-shaped inlet cavity 40 with an O.D. ofabout 2,300 microns, and a depth of about 5.65 microns; having aring-shaped regulator seat 42 with a width (as measured between its I.D.and O.D.) of about 750-2,000 microns; having an initial regulator gap 48height (when the driving pressure difference (P) is equal to zero) inthe range of about 2-3 microns; having an outlet cavity 52 about 5.65microns deep; and having an outlet port 54 with a minimum diameter ofabout 100 microns and a length of about 494 microns, it has beendiscovered that (m) is on the order of about 2.4 and (n) is on the orderof about 2/3.

The second strategy which may be used to assist in designing a radialflow regulator 32 which has any particular desired flow regulationcharacteristics is to develop a sophisticated physical model usingnumerical methods.

The starting point for formulating the model may be that, for anyparticular radial flow regulator 32, the flow of the medication 12through it may be generally governed by the following equation: ##EQU2##where (Q), (P), and (R_(s)) are as has been defined above; where(R_(ch)) is the combined flow resistance across the radial inletchannels 38; where (R_(ch)) is a direct function of the length (L) andthe wetted perimeter (C) of each of the radial inlet channels 38; where(R_(ch)) is an inverse function of the cross-sectional area (A) of eachof the radial inlet channels 38; and where (R_(s)) is a nonlinearfunction of the flow rate (Q).

That is, the flow rate (Q) is proportional to the driving pressuredifference (P), and is inversely proportional to the sum of the two flowresistances (R_(ch)) and (R_(s)). A circuit diagram illustrating thisbehavior is shown in FIG. 4.

It has been found that accurate prediction of the nonlinear flowresistance (R_(s)) of the regulator gap 48 may require the considerationof at least the following four factors.

First, the nonlinear flow resistance (R_(s)) of the regulator gap 48 maybe a function of the pressure drop across the inlet channels 38, due totheir flow resistance (R_(ch)). This is because the greater the pressuredrop across the inlet channels 38, the greater the driving pressuredifference (P) across the flexure 28, and the greater the amount of thedeflection of the flexure 28 (and vice versa). This, in turn, generallydecreases the height of the regulator gap 48; thereby generallyincreasing the flow resistance (R_(s)) of the regulator gap 48 (and viceversa). However, such deflection of the flexure 28 is not uniform, sincethe deflected flexure 28 is not flat, but instead assumes a convex, orbowed shape. This results in the nonlinear flow resistance (R_(s)) ofthe regulator gap 48 being a relatively complex function of the flowresistance (R_(ch) ) of the inlet channels 38.

Second, the nonlinear flow resistance (R_(s)) of the regulator gap 48may be a function of the viscous shear forces of the medication 12acting on the flexure 28's bottom surface 50 as the medication 12 flowsradially inwardly through the regulator gap 40, from the inlet cavity 40to the outlet cavity 52. Such viscous shear forces are, in turn, afunction of such things as the viscosity and velocity of the medication12 in the regulator gap 48. Such viscous shear forces are directedradially inwardly on the flexure 28's bottom surface 50, and tend totwist or distort the flexure 28's bottom surface 50 with respect to theflexure 28's top surface 62. Such twisting or distorting of the flexure28 tends to vary the size and shape of the regulator gap 48 which, inturn, varies the flow resistance (R_(s)) of the regulator gap 48. Thisresults in the nonlinear flow resistance (R_(s)) of the regulator gap 48being a relatively complex function of the viscous shear forces of themedication 12 acting on the flexure 28.

Third, the nonlinear flow resistance (R_(s)) may be a function of thevelocity of the medication 12 passing through the regulator gap 48. Suchvelocity is, in turn, a function of such factors as the flow resistance(R_(ch)) of the inlet channels 38; the driving pressure difference (P)across the regulator 32; the height, size and shape of the regulator gap48; and the flow resistance (R_(s)) of the regulator gap 48.

Because of the Equation of Continuity and Bernoulli's Equation, as thevelocity of the medication 12 through the regulator gap 48 increases,the pressure of the medication 12 within the regulator gap 48 tends todecrease (and vice versa). This is because the Equation of Continuityrequires that the velocity of the medication 12 must increase at arestriction. Thus, since the regulator gap 48 is a restriction (ascompared to the inlet cavity 40), the velocity of the medication 12 mustincrease as it flows through the regulator gap 48. Bernoulli's equationthen requires that the pressure of the medication 12 in the regulatorgap 48 must fall, due to its increased velocity as it flows through theregulator gap 48.

That is, as the velocity of the medication 12 in the regulator gap 48increases, the pressure of the medication 12 in the regulator gap 48decreases. This increases the amount of the deflection of the flexure28; which, in turn, generally decreases the height of the regulator gap48 and increases the flow resistance (R_(s)) (and vice versa).

Fourth, the nonlinear flow resistance (R_(s)) may be a function of theflexure 28's thickness, resiliency, elasticity and stiffness. This isbecause for any given forces acting on the flexure 28, the amount of thedeflection of the flexure 28, and the shape (or radial profile) of thedeflected flexure 28, may be a function of the flexure 28's thickness,resiliency, elasticity and stiffness.

In the forgoing discussion, it was assumed that the membrane 36's inletchannel cover portions 30 were selected such that they would not bedeflected a substantial amount downwardly into the inlet channels 38 bythe medication 12 during the operation of the radial flow regulator 32.Thus, the forgoing discussion assumed that substantially none of theregulation of the flow of the medication 12 by the flow regulator 32 wasdone by any such deflection of the 36's inlet channel cover portions 30.

However, this need not be the case since, as will be made apparent byall of the disclosures in this document, regulation of the flow rate (Q)of the medication 12 through the radial flow regulator 32 may be atleast partially done by such deflection of the membrane 36's inletchannel cover portions 30.

From the forgoing, it is seen that the primary difficulty in developinga sophisticated physical model for the radial flow regulator 32 whichuses numerical methods is that the amount of the deflection or bow ofthe flexure 28, and the shape of the flexure 28 as it deflects or bows,are closely coupled and nonlinear in interaction. As a result, iterativetechniques may be used to generate a solution for the flexure 28'sdeflected or bowed shape (a) that is correct at every point of contactbetween the medication 12 and the flexure 28 in terms of the forcesapplied to the flexure 28; and (b) that simultaneously provides aconsistent radial gradient of the driving pressure difference (P) of themedication 12 across the flexure 28 which obeys the laws of fluid flow.

To do this, a free body diagram may first be developed for an arbitraryring-shaped segment of the flexure 28. This model creates the followinggoverning fourth-order differential equation set that identifies therelationship between the flexure 28's local curvature and its thickness;Young's modulus and Poisson's ratio; and exterior forcing functions thatinclude the shear between the medication 12 and the flexure 28, anydriving pressure difference (P) across the flexure 28, and the flexure28's radial tension. The governing fourth-order differential equationset may be determined in the following way.

The first derivative of the deflection (θ) of the flexure 28 towards theregulator seat 42 is given by the following second order differentialequation: ##EQU3## where r is radial position with respect to the centerof the flexure 28; ΔP(r) is the driving pressure difference across theflexure 28 at the radial position r; and D_(t) is given by: ##EQU4##where E is Young's Modulus; t is the thickness of the flexure 28; and νis Poisson's ratio.

The actual deflection Y(r) of the flexure 28 is obtained by integratingabove Equation 1: ##EQU5## where Y_(o) is the centerline deflection ofthe flexure 28. Hence the governing differential equation set is fourthorder.

Next, a first-order differential equation may be developed for theflexure 28's driving pressure difference (P) pressure drop across theannular ring-shaped portion of the regulator gap 48 which is directlyunder the above mentioned arbitrary ring-shaped segment of the flexure28. This differential equation must take into account not only thechange in the regulator gap 48 caused by the amount of the deflection orbowing of the flexure 28, but also any change in the regulator gap 48caused by the substrate 34's inlet channels 38 and inlet cavity 40. Thefirst-order differential equation for the driving pressure differenceΔP(r) is: ##EQU6## where ΔP₁ is the driving pressure difference (P) atthe outer rim of the inlet cavity 40, referenced to the constantpressure of the medication 12 external to the flexure 28; Q is thevolumetric flow rate of the medication 12; μ is the viscosity of themedication 12; and H(r) is the height of the regulator gap 48 when thedriving pressure difference (P) is equal to zero.

In short, the above Equation 2 describes the amount and shape of thedeflection or bowing of the flexure 28; while the above Equation 3provides a means to calculate the driving pressure difference (P) of themedication 12 across the flexure 28 at any radial position with respectto the flexure 28. To be a physically correct representation of theinteraction between the driving pressure difference (P) across theflexure 28, and the amount and shape of the deflection or bowing of theflexure 28, the solutions of the above Equations 2 and 3 must beconsistent with each other in a point-to-point sense across the entireradius of the flexure 28.

To achieve this goal, the above Equation 2 may be converted to a finitedifference form, and a guess may be made as to the radial profile of thedriving pressure difference (P) of the medication 12 across the flexure28. This is necessary since a solution of the bowing or deflectedflexure 28's above Equation 2 requires knowledge of the driving pressuredifference (P) of the medication 12 across the flexure 28 at each radialposition.

This results in a so-called tridiagonal array of coupled equations thatmay be solved recursively for the flexure 28's radial slope at eachpoint. Then this may be integrated once to yield the flexure 28'sdeflection at each radial position. Once this is known, the radialprofile of the driving pressure difference (P) across the flexure 28 maybe recalculated using these new deflection values for the flexure 28 byintegration of the above Equation 3.

The above iterative process may then be continued, as necessary, untilthe calculated position of the flexure 28 does not change by somearbitrarily set small amount per iteration, thereby signalling aconsistent solution set.

Any number of different cylindrically-symmetric fluid flow devices maybe modeled with the above equation set. By changing the sign of Q, bothinward and outward flow of the medication 12 through the devices may bemodeled. By adjusting the function H(r) to reflect the height of the gapbetween the particular fluid flow device's flexure and the correspondingpart of its substrate, the above equation set may be equally useful formodeling flow switches (such as the flow switch 250), one-way valves(such as the one-way valves 210, 240, 300), and other flow regulators(such as the flow regulators 80, 110). In the particular case of one-wayvalves (such as the one-way valve 300), in which there is a pre-setinterference or prestressing between the seat 310 and the flexure 314,that is, the seat 310 protrudes above the plane of the flexure 314'sbottom surface 322, it is only necessary to initiate solution of thecoupled equations with a trial deflected shape of the flexure 314 thatclears the seat 310 and allows the medication 12 to begin to flowradially inwardly across the seat 310.

FIG. 5 shows the above mathematical model being used to predict theresponse of a typical design for the flow regulator 32. The solid curve72 in FIG. 5 shows a plot of the above mathematical model for the radialflow regulator 32, in terms of flow of the medication 12 through theregulator 32 in μL/day as a function of the driving pressure difference(P) across the flexure 28.

The diamond-shaped data points 74 which are plotted in FIG. 5 are for atypical radial flow regulator 32 having a radial array of fourrectangular inlet channels 38, each having a width of about 70 microns,a length of about 1270 microns, and a depth of about 5.7 microns; aninlet cavity having a maximum diameter of about 2290 microns, and adepth of about 5.7 microns; a regulator seat 42 having an I.D. of about508 microns, and an O.D. of about 1780 microns; a flexure manufacturedfrom a membrane of silicon having a thickness of about 25 microns; aregulator gap 48 having a height of about 2.5 microns (when the drivingpressure difference (P) across the flexure 28 is zero); an outlet cavityhaving a diameter of about 508 microns, and a depth of about 5.7microns; and an outlet port having a minimum diameter of about 100microns, and a length of about 494 microns.

The dashed curve 76 is an empirical curve which is derived by applyingcurve-fitting techniques to the plotted data points 74. As seen in FIG.5, agreement between the theoretical curve 72 and the plotted datapoints 74 is very good.

The curve 78 in FIG. 6 shows the above mathematical model being used topredict the reduction in the medication 12's flow rate setpoint(Q_(set)) caused by sealing off the four inlet channels 38 one-by-one.The diamond-shaped data points 74 which are plotted in FIG. 6 are for atypical radial flow regulator 32 having the physical parameters whichwere set forth above.

As seen in FIG. 6, when one inlet channel 38 is sealed off, theeffective combined flow resistance (R_(ch)) of the remaining threechannels 38 increases by about 33%, as compared to the combined flowresistance (R_(ch)) of the original array of four inlet channels 38.Similarly, plugging two and three of the inlet channels 38 will increasethe effective combined flow resistance (R_(ch)) of the remaining inletchannel(s) 38 by about 100% and about 400%, respectively. As seen inFIG. 6, the mathematical model curve 78 predicts this behavior of theradial flow regulator 32 very well.

The qualitative effect of closing off one or more of the inlet channels38 is to increase the driving pressure difference (P) across the flexure28 which is needed for any given flow rate (Q) of the medication 12through the radial flow regulator 32. This causes the flexure 28 to comeinto closer proximity to the regulator seat 42 at a lower flow rate (Q),and hence biases the regulator 32's flow rate setpoint (Q_(set)) to avalue for the flow rate (Q) which is lower than would otherwise be thecase.

It has been discovered that, as seen in FIG. 3, as the number of theinlet channels 38 is decreased, the "control zone" of the flow rate (Q)occurs at lower and lower flow rates (Q) for any given driving pressuredifference (P) across the radial flow regulator 32. It has also beendiscovered that, as is also seen in FIG. 3, as the number of the inletchannels 38 is decreased, there may be a reduced sensitivity in the rateof change of the flow rate (Q) for any given change in the drivingpressure difference (P) in the "control zone" of the flow rate (Q).However, the theoretical grounds for this behavior of the regulator 32are not clear, and it is possible that this behavior may be due to anartifact in a regulator 32 which is imperfect.

All of the forgoing is very important, since it has been discovered thata single radial flow regulator 32 may actually have the properties offour different regulators 32, depending on whether none, one, two orthree of its inlet channels 38 are sealed. That is, as seen in FIG. 3,such regulators 32 have quite different regulation curves 64, 66, 68,70; have quite different "control zones" and flow rate set points(Q_(set)); have quite different flow rates (Q) for any given drivingpressure difference (P); and have quite difference sensitivities tochanges in their flow rates (Q) for any given change in the drivingpressure difference (P).

This makes the present invention much more versatile, since a singleradial flow regulator 32 may be easily modified to do the work of foursingle-function flow regulators. Of course, as was mentioned above,there may be fewer, or more, than four inlet channels 38; so one radialflow regulator 32 may be easily modified to do the work of fewer or moresingle-function flow regulators 32.

From the disclosures in this document, it is possible to selectivelydesign a radial flow regulator 32 for any particular desired flowregulation characteristics or driving pressure difference (P). This maybe done by selectively adjusting one or more of the pertinentparameters, such as: (a) the number, length, size, and cross sectionalconfiguration of the radial inlet channels 38; (b) the number, size,cross-sectional configuration and location of the cavities 40, 52 andthe outlet port 54; (c) the number, size, cross-sectional configurationand height of the regulator seat 42; (d) the number, size,cross-sectional configuration and height of the regulator gap 48; and(e) the thickness, resiliency, elasticity and stiffness of the membrane36.

For example, it has been discovered that by adjusting the fraction ofthe driving pressure difference (P) that is dropped across the radialinlet channels 38 in relation to the fraction of the driving pressuredifference (P) which is dropped across the regulator gap 48 (byadjusting the flow resistance (R_(ch)) of the inlet channels 38 and theflow resistance (R_(s)) of the regulator gap 48 with respect to eachother), two things may be selectively modified. First, the degree ofcontrol of the regulator flow (Q) versus the driving pressure difference(P) may be selectively varied; and second, the amount of regulator flow(Q) versus the driving pressure difference (P) may also be selectivelyvaried.

MICROMACHINED RADIAL FLOW REGULATOR 32 (FIGS. 1-6): MANUFACTURE

The substrate 34 may be manufactured from any suitable strong, durablematerial which is compatible with the medication 12, and in which theinlet channels 38, the inlet cavity 40, the regulator seat 42, theoutlet cavity 52, and the outlet port 54 may be manufactured in anysuitable way, such as by using any suitable etching, molding, stampingand machining process. Such a machining process may include the use ofphysical tools, such as a drill; the use of electromagnetic energy, suchas a laser; and the use of a water jet.

The membrane 36 may be manufactured from any suitable strong, durable,flexible, material which is compatible with the medication 12.

If the radial flow regulator 32 is intended to regulate a medication 12which is to be supplied to a human or an animal, then any part of theregulator 32 which is exposed to the medication 12 should bemanufactured from, and assembled or bonded with, non-toxic materials.Alternatively, any toxic material which is used to manufacture theregulator 32, and which is exposed to the medication 12 during use ofthe regulator 32, may be provided with any suitable non-toxic coatingwhich is compatible with the medication 12.

Suitable materials for the substrate 34 and the membrane 36 may bemetals (such as titanium), glasses, ceramics, plastics, polymers (suchas polyimides), elements (such as silicon), various chemical compounds(such as sapphire, and mica), and various composite materials.

The substrate 34 and the membrane 36 may be assembled together in anysuitable leak-proof way. Alternatively, the substrate 34 and themembrane 36 may be bonded together in any suitable leak-proof way, suchas by anodically bonding them together; such as by fusing them together(as by the use of heat or ultrasonic welding); and such as by using anysuitable bonding materials, such as adhesive, glue, epoxy, solvents,glass solder, and metal solder.

Anodically bonding the substrate 34 and the membrane 36 together may bepreferable for at least four reasons. First, anodic bonding isrelatively, quick, easy and inexpensive. Second, an anodic bond providesa stable leak-proof bond.

Third, since an anodic bond is an interfacial effect, there is nobuild-up of material at the bond; and the bond has essentially a zerothickness, which desirably creates no essentially no spacing between thesubstrate 34 and the membrane 36. As a result, an anodic bond does notinterfere with the desired height of the regulator gap 32.

Fourth, an anodic bond may be preferable since it eliminates the needfor any separate bonding materials, which might otherwise clog or reducethe size of the inlet channels 38, the inlet cavity 40, the regulatorseat 42, the regulator gap 48, the outlet cavity 52, and the outlet port54; or which might lead to corrosion of the joint between the regulator32's substrate 34 and membrane 36.

One example of how the radial flow regulator 32 may be manufactured willnow be given. The starting may be a 76.2 mm diameter wafer of Corning7740 Pyrex glass, which will form the regulator 32's substrate 34.

The glass wafer may be cleaned in any suitable way, such as by immersingit in a buffered hydrofluoric acid (BHF) etchant for two minutes,rinsing it with distilled water, and drying it.

A thin chrome metallization layer may then applied to the top surface ofthe glass wafer by any suitable means, such as with an electron beamevaporator. The chrome layer may provide a good adhesion surface for thesubsequent application of photosensitive resist (photoresist) to theglass wafer's top surface.

Following this, a thin layer of any suitable photoresist may be appliedon top of the chrome layer, such as Microposit 1650 photoresist made bythe Shipley Company, located in Newton, Mass. The layer of photoresistmay be dried in any suitable way, such as by baking it at about 90° C.for about 25 minutes.

An image of the four radial inlet channels 38, the inlet cavity 40, andthe outlet cavity 52 may then be exposed onto the photoresist in anysuitable manner, such as by using a first mask and a mask aligner. Thisimage may be developed (that is, the exposed photoresist may beremoved), by using any suitable photoresist developer, such as 351developer, made by the above Shipley Company. The glass wafer may thenbe then rinsed in distilled water and dried.

As a result of the forgoing procedure, the chrome layer will now bear animage, unprotected by the photoresist, of the four radial inlet channels38, the inlet cavity 40, and the outlet cavity 52. The unprotectedportions of the chrome layer may then be removed by using any suitablechrome etch solution, such as Cyantek CR-7, made by the Cyantek Company,located in Fremont, Calif.

The forgoing procedure will result in an image of the four radial inletchannels 38, the inlet cavity 40, and the outlet cavity 52 having beenformed on the top surface of the glass wafer, which image is unprotectedby the layers of photoresist and chrome which cover the rest of theglass wafer's top surface. The image may then be etched into the glasswafer's top surface to any desired depth by any suitable means, such asby immersing the glass wafer's top surface in BHF etchant; rinsing theglass wafer in distilled water, and drying it. A suitable depth may beabout 6.0 microns.

Next, an image of the regulator seat 42 may then be exposed onto thephotoresist on the glass wafer's top surface using a second mask. Thenewly exposed photoresist may then be developed; and the newly exposedportions of the chrome removed. Then the image of the regulator seat maybe etched into the top surface of the glass wafer to any desired depthin any suitable manner, in order to define an elevation differencebetween the regulator seat 42's top surface 44 and the top surface ofthe glass wafer. A suitable elevation difference may be about 2.5microns.

At this point, it may be noted that the depths of the four radial inletchannels 38, the inlet cavity 40, and the outlet cavity 52 will alsohave been automatically increased by about 2.5 microns, since they arealso unprotected by the layers of chrome and photoresist. In otherwords, the four radial inlet channels 38, the inlet cavity 40, and theoutlet cavity 52 may intentionally be initially etched to a depth lessthan their desired final depth, in order to permit them to automaticallyand simultaneously reach their desired final depth while the regulatorseat 42 was being etched.

Note that the above procedure is unusually economical and quick, sinceif the four radial inlet channels 38, the inlet cavity 40, and theoutlet cavity 52 were originally etched to their desired final depth,then the additional steps of re-coating the entire glass wafer withphotoresist (in order to protect the etched four radial inlet channels38, the inlet cavity 40, and the outlet cavity 52), and then baking thephotoresist, would have to be done prior to the exposing, developing andetching of the regulator seat 42.

After the regulator seat 42 has been etched, the regulator 32's outletport 54 may be formed by any suitable means, such as by drilling it witha focused beam from a 25 W CO₂ laser, with a physical drill, or with awater jet drill. It has been discovered that when using a laser to formthe outlet port 54, heating the glass wafer to near its anneal pointimproves the quality of the outlet port 54, and also reduces undesirablecracking of the glass wafer adjacent to the outlet port 54.

Preferably, as seen in FIG. 2, the outlet port 54 may have aventuri-like shape, rather than being cylindrical in shape, for betterfluid flow through it. It has also discovered that the outlet port 54may be given its preferred venturi-like shape by drilling the outletport 54 with a laser in the manner discussed above. The desiredventuri-like shape may be automatically formed during the laser drillingprocess, and apparently results from the thermal effects of the laserbeam interacting with the glass wafer as the outlet port 54 is beingdrilled through it with the laser beam. After the outlet port 54 hasbeen drilled, the glass wafer may be lightly etched with BHF etchant, inorder to remove any volatilized glass which may have condensed on theglass wafer adjacent to its outlet port 54.

After the outlet port 54 has been formed, a nominal layer of one or morecorrosion-resistant substances may be deposited onto the top surface ofthe glass wafer by any suitable means, such as by sputtering using ane-beam evaporator. As a result, the four radial inlet channels 38, theinlet cavity 40, the regulator seat 42, the outlet cavity 52, and theoutlet port 54 will have been coated with a layer of thecorrosion-resistant substance(s).

Suitable corrosion-resistant substances may be silicon, or may bemetals, such as gold, platinum, chrome, titanium and zirconium, or maybe the oxides of silicon or such metals. Such oxides may be formed bythermally oxidizing the corrosion-resistant substance(s) in air after ithas been applied to the substrate 34. However, other suitablecorrosion-resistant substances may be used, depending on the particularmedication 12 with which the radial flow regulator 32 is designed to beused. The oxides of metals such as titanium and zirconium are well-knownto be stable against water solutions over a wide pH range. The thicknessof the layer of the corrosion-resistant substance(s) may be from 200Å-1000 Å; but the thickness may depend on the particularcorrosion-resistant substance(s) being used, and on the particularmedication 12 with which the radial flow regulator 32 is designed to beused.

Alternatively, the layer of corrosion-resistant substance(S) maycomprise a donut-shaped disk of such corrosion-resistant substance(s),such as silicon, which may be bonded to the regulator seat 42's topsurface 44 by any suitable means, such as by using any of the meanswhich have been mentioned for bonding the substrate 34 and the membrane36 together.

Such a corrosion-resistant donut-shaped disk may be formed in anysuitable way, such as by using a masking and etching process which issimilar to that described above regarding the substrate 34. The startingpoint may be a clean epitaxial-coated silicon wafer, to which is applieda thin chrome metallization layer and a layer of photoresist. After thephotoresist is dry, an image of the donut-shaped disk may then beexposed onto the photoresist. The exposed photoresist, and theunderlying portions of the chrome layer, may then be removed, resultingin an image of the donut-shaped disk on the surface of the siliconwafer, which image is not protected by the photoresist or by the chromelayer. The exposed portions of the silicon wafer may then etched to adepth in excess of the desired thickness of the desired donut-shapeddisk in any suitable way, such as by the use of an isotropic siliconetchant. For example, if a donut-shaped disk having a thickness of about1 micron was desired, then the exposed portions of the silicon wafer maybe etched to a depth of about 5 microns.

The silicon wafer may then be cleaned; the etched faces of the siliconand glass wafers may then be aligned with each other, so that thedonut-shaped disk on the silicon wafer is aligned with the regulatorseat 42 on the glass wafer; and the silicon and glass wafers may then bebonded together in any suitable way, such as by using an anodic bondingprocess like that which will be described below regarding anodicallybonding together the silicon and glass wafers that will form theregulator 32's substrate 34 and membrane 36. Next, the silicon waferwith the donut-shaped disk may then etched again in any suitable way,such as by the use of an anisotropic ethylene diamine etchant, until thedesired ultimate thickness of the donut-shaped disk of silicon isobtained.

The manufacture of only one substrate 34 and only one donut-shaped diskof corrosion-resistant material for the substrate 34's regulator seat 42was described above. However, it will be appreciated that on any pair ofglass and silicon wafers respective arrays of substrates 34 andcorresponding donut-shaped disks of corrosion-resistant material may bemanufactured simultaneously in a manner which is similar to thatdescribed above. If such is the case, the array of substrates 34 on theglass wafer may be aligned with, and then bonded to, the correspondingarray of donut-shaped disks of corrosion-resistant material on thesilicon wafer. After the final etching of the silicon wafer, themanufacture of each regulator 32 may then be completed in the mannerwhich is set forth below.

If a donut-shaped disk or layer of corrosion-resistant substance(s) isbonded or applied to the regulator seat 42, then the regulator seat 42may have to be etched an additional amount during its above etching stepprior to applying the donut-shaped disk or layer of corrosion-resistantsubstance(s) to the regulator seat 42's top surface 44. The additionalamount of etching may be equal to the thickness of the donut-shaped diskor layer, in order to end up with the desired elevation differencebetween the regulator seat 42's top surface 44 and the top surface ofthe glass wafer (which will form the substrate 34).

It has been discovered that the donut-shaped disk or layer ofcorrosion-resistant substance(s) on the regulator seat 42's top surface44 may serve an unexpected further function in addition to itscorrosion-resistant function. That is, it may also prevent the regulator32's membrane 36 from being inadvertently bonded to the regulator seat42's top surface 44 when the membrane 36 is being bonded to the glasswafer, such as when the membrane 36 is being anodically bonded in themanner which will be described below.

After the regulator seat 42 has been etched, and after any desired layeror disk of corrosion-resistant substance(s) has been applied to etchedportions of the glass wafer, the photoresist and chrome which remain onthe unetched portions of the glass wafer may be removed by any suitablemeans, such as by using standard lift-off techniques.

Fabricating the membrane 36 and mounting it to the glass wafer (which isthe substrate 34), may be done in any suitable way.

One suitable way is to start with a prime silicon wafer having aboron-doped epitaxial silicon layer which has been deposited onto itstop surface. Since the boron doped epitaxial silicon layer willultimately form the regulator 32's membrane 36, the layer's thicknesswill depend on the desired thickness of the membrane 36. The boron-dopedepitaxial silicon layer, and thus the membrane 36, may be from 1-50microns thick, for example. The boron doping may be in excess of 3×10¹⁹atoms of boron per cubic centimeter, which conveys a dramaticetch-resistance to the epitaxial silicon layer in silicon etchants basedon ethylene diamine.

The glass and silicon wafers may then be cleaned; dried; and anodicallybonded together. The anodic bonding may be performed in any suitableway, such as by placing the respective top surfaces of the glass andsilicon wafers in contact with each other in a vacuum chamber in an ovenmaintained at a temperature of about 500° C. A DC voltage ofapproximately 1000 volts may then be applied to the two wafers for aperiod of about 15 minutes, with the silicon wafer at a positivepotential relative to the bottom surface of the glass wafer. Anexponentially decaying current will flow through the wafers over thistime period, at the end of which the two wafers will have beenanodically bonded together, i.e., they will have been hermeticallybonded to each other to form a silicon/glass sandwich. It has also beendiscovered that the anodic bonding process may also ensure that anycorrosion-resistant substance(s) which were applied to the etchedsurfaces of the glass wafer are firmly attached to it.

Upon cool-down, after the anodic bonding process is complete, thesilicon wafer portion of the anodically bonded silicon/glass sandwichmay be ground down; but preferably, the silicon wafer is not ground downso much that any of its boron doped epitaxial silicon layer is removed.For example, if the boron doped epitaxial silicon layer is from about1-50 microns in thickness, then the silicon wafer portion of the bondedsilicon/glass wafer sandwich may be ground down to about 125 microns inthickness. The remaining non-doped silicon in the silicon wafer may thenbe removed in any suitable way, such as by placing the ground downsilicon/glass sandwich in an ethylene diamine etchant maintained at 112°C. for 3.5 to 4.0 hours. A suitable ethylene diamine etchant may bePSE-300, manufactured by the Transene Corp. located in Rowley, Mass. Atthe end of this time, the boron doped epitaxial silicon layer will beexposed in the form of a continuous, flat membrane 36 which isanodically bonded to the glass wafer (the substrate 34), thereby formingthe completed radial flow regulator 32, which is then cleaned and dried.

The purpose of the above grinding step is simply to reduce the amount ofsilicon which needs to be etched away. Accordingly, as alternatives, thegrinding step may be eliminated, with all of the undesired silicon beingetched away; or a thinner silicon wafer may be used, so that there isless undesired silicon to begin with.

The manufacture of only one radial flow regulator 32 was describedabove. However, it will be appreciated that on any pair of glass andsilicon wafers numerous regulators 32 could be manufacturedsimultaneously in a manner similar to that described above. If such isthe case, an array of substrates 34 may be simultaneously etched in theglass wafer before the silicon and glass wafers are aligned and bondedtogether. Then, all of the membranes 36 may be formed simultaneously bygrinding and etching the silicon wafer to its desired final thickness.The silicon/glass sandwich may then be divided by any suitable means(such as dicing) into individual chips, each chip bearing at least oneradial flow regulator 32.

One of the advantages of using the etching and anodic bonding processwhich was described in detail above is that such a process enables highquality, very reliable radial flow regulators 32 to be mass produced ingreat numbers at a cost so low that the regulator 32 may be consideredto be disposable. In addition, it should also be noted that theregulator 32 is stunning in its simplicity since it may have as few asonly two parts (the substrate 34 and the membrane 36); and since it mayhave only one moving part (the membrane 36's flexure 28). Further,because the raw materials from which the regulator 32 may bemanufactured may be very inexpensive, such as glass and silicon, thecost of the regulator 32 may held to a very low level.

MICROMACHINED LINEAR FLOW REGULATOR 80 HAVING A CONTOURED REGULATOR SEAT90 (FIGS. 7-12): STRUCTURE

Turning now to FIGS. 7-8, the micromachined linear flow regulator 80 ofthe present invention is illustrated. The linear flow regulator 80 maybe used to control the flow rate of a fluid medication 12 passingthrough it, and may comprise a substrate 82, and a membrane 84. Thesubstrate 82 may include a straight, elongated channel 86 having acontoured regulator seat 90 and an outlet port 92. The membrane 84 mayhave a mounting portion 97, which is mounted to a corresponding portionof the substrate 82's top surface 96; an inlet port 94; and a flexure 98which overlies the channel 86. A regulator gap 99 lies between theflexure 98 and the regulator seat 90.

Although only one outlet port 92 in the substrate 82 is illustrated,there may be more outlet ports 92. Although, as seen, the outlet port 92is preferably located near one end of the channel 86, so that duringoperation of the regulator 80 the downwardly deflecting flexure 98 willnot seal off the outlet port 92, each outlet port 92 may be positionedin any other suitable location in the channel 86. Although preferablythe outlet port 92 may have a venturi-like shape, for better flow of themedication 12 through it, the outlet port 92 may have any other suitableshape. Although the outlet port 92 is illustrated as being located inthe substrate 82, the outlet port 92 may be wholly or partially locatedin the membrane 84.

Although the channel 86 and the regulator seat 90 which are illustratedin FIGS. 7-8 follow a straight course, the channel 86 and the regulatorseat 90 may follow a circular (FIG. 9), spiral (FIG. 10), serpentine(FIG. 11), or other non-straight course. The use of a regulator 80having a channel 86 and a regulator seat 90 which follow a circular,spiral, serpentine, or other non-straight course may be desirable. Thisis because, for any given length of channel 86 and regulator seat 90,such courses may permit the manufacture of a linear regulator 80 whichis more compact, as compared to a linear regulator 80 having a straightchannel 86 and regulator seat 90.

Preferably, the contour of the regulator seat 90 may approximate, orduplicate, the contoured shape that the flexure 98 would assume if theflexure 98 were entirely unrestrained by any part of the substrate 82when the linear flow regulator 80 is subjected to the regulator 80'smaximum designed driving pressure difference (P) of the medication 12between the regulator 80's inlet port 88 and outlet port 92.

Although the membrane 84 is illustrated as being of uniform thickness,and as having flat top and bottom surfaces 100, 101, the membrane 84 maynot be of uniform thickness, and may have top and bottom surfaces 100,101 which are not flat.

Although the membrane 84 shown has one rectangular inlet port 88, theremay be more than one inlet port 88, and each inlet port 88 may have anyother suitable shape. Although the inlet port 88 is illustrated as beingin the membrane 84, the inlet port 88 may be wholly or partially locatedin the substrate 82.

By way of example, the linear flow regulator 80's substrate 82 may bemanufactured from 7740 Pyrex glass, and may have a thickness of about0.5 mm. The channel 86 and the regulator seat 90 may each have a lengthof about 10 mm, and a maximum width of about 480 microns. The regulatorgap 99 may have a maximum height of about 6.65 microns (when the drivingpressure difference (P) is equal to zero). The outlet port 92 may have aminimum diameter of about 100 microns, and may have a length of about496 microns. The membrane 84 may be manufactured from silicon, and mayhave a thickness of about 4.0 microns. The inlet port 88 may have awidth of about 480 microns, and a length of about 500 microns. The flowcharacteristics of this example linear flow regulator 80 are illustratedin FIG. 12, which will be discussed below.

Turning now to FIGS. 9-11, the linear flow regulators 80 illustratedtherein are the same as, or at similar to, the linear flow regulator 80of FIGS. 7-8, in their structure, operation, theory, and manufacture,except for those differences, if any, which will be made apparent by anexamination of all of the Figures and disclosures in this document.Accordingly, the respective parts of the linear flow regulators 80 ofFIGS. 9-11 have been given the same reference numerals as thecorresponding parts of the linear flow regulator 80 of FIGS. 7-8, forclarity and simplicity.

One of such differences is that the linear flow regulators 80illustrated in FIGS. 9 and 11 have a pair of outlet ports 92, instead ofthe single outlet port 92 of the regulator 80 of FIGS. 7-8. Other ofsuch differences are that the channel 86 and the regulator seat 90 ofthe regulator 80 illustrated in FIGS. 7-8 follow a straight course,while the channels 86 and the regulator seats 90 of the regulators 80 ofFIGS. 9-11 follow a circular, spiral, and serpentine course,respectively.

As will be appreciated from all of the disclosures in this document, thefact that the linear flow regulators 80 may, as in the example set forthabove, have an extremely small size, be extremely light weight, haveonly two parts, and have a zero electrical energy consumption, offernumerous advantages over a regulator 80 which was physically muchlarger, much heavier, more complex, or which consumed electrical energy.For example, the regulators 80 may be ideal for use as part of aminiaturized medication delivery device which is to be implanted in ahuman or animal for delivery of constant flows of the medication 12 atflow rates as low as about 0.01 cc/day--flow rates which are so low thatthey may be impossible for a physically larger flow regulator of adifferent design to reliably and accurately deliver.

MICROMACHINED LINEAR FLOW REGULATOR 80 HAVING A CONTOURED REGULATOR SEAT90 (FIGS. 7-12): OPERATION AND THEORY

The linear flow regulator 80 may be installed in its intended locationof use in any suitable way. Any suitable medication supply means may beused to connect the regulator 80's inlet port 88 to a source of themedication 12; and any suitable medication delivery means may be used toconnect the regulator 80's outlet port 92 to whatever person, animal orthing is to receive the medication 12 from the outlet port 92. In somecases, the medication supply means may also be used to supply themedication 12 to the flexure 98's top surface 100, at a pressure whichmay or may not be the same as the pressure at which the medication 12 issupplied to the inlet port 88.

For example, the regulator 80 may be installed within any type ofreservoir means for the medication 12 by any suitable means, such as bylocating the regulator 80's outlet port 92 over the reservoir means'soutlet, and by using an adhesive face seal between the regulator 80'sbottom surface 104 and the inside of the reservoir means to hold theregulator 80 in place. As a result, when the reservoir means is filledwith the medication 12, the regulator 80 will be immersed in themedication 12, with its inlet port 88 and its flexure 98's top surface100 in fluid communication with the medication 12 within the reservoirmeans, and with its outlet port 92 in fluid communication with thereservoir means' outlet. Such an installation for the regulator 80 hasnumerous advantages.

For example, it is quick, easy, reliable and inexpensive, because noadditional medication supply means (such as supply conduits) are neededto supply the medication 12 to the regulator 80's inlet port 88 and tothe flexure 98's top surface 100 (since they are already immersed in themedication 12); and because no additional medication delivery means(such as delivery conduits) are needed to convey the medication 12 awayfrom regulator 80's outlet port 92 (since the reservoir means' outlet isused for this purpose). Such additional inlet and outlet conduits may beundesirable since it may be relatively time consuming, difficult andexpensive to align and connect them to regulator 80, due to theextremely small size of its inlet port 88, flexure 98, and outlet port92. Such additional inlet conduits may also be undesirable because theymay tend to trap a bubble when being filled with a liquid medication 12,which bubble might then be carried into the regulator 80 and cause it tomalfunction.

In the discussion which follows it will be assumed, for clarity andsimplicity, that during operation of the regulator 80, the flexure 98'stop surface 100 and the inlet port 88 are both exposed to a pressurizedsource of the medication 12 from the medication supply means. It willalso be assumed, for clarity and simplicity, that the driving pressuredifference (P) of the medication 12 across the regulator 80 is thepressure difference between the medication 12 at the flexure 98's topsurface 100, and the medication 12 at the outlet port 92; which is thesame as the pressure difference between the medication 12 at theentrance of the inlet port 88 and the outlet port 92. However, it isunderstood that during operation of the regulator 80, these pressuredifferences need not be equal, and the flexure 98's top surface 100 doesnot necessarily have to be exposed to the pressurized source of themedication 12 from the medication supply means.

During operation, as a driving pressure difference (P) is applied acrossthe regulator 80, such as by pressurizing the source of the medication12 with respect to the regulator 80's outlet port 92 by any suitablemeans, the medication 12 will pass sequentially through the regulator80's inlet port 88, regulator gap 99, and outlet port 92.

Referring now to FIG. 12, the regulator curve 106 is illustrated for theregulator 80. The regulator curve 106 is a plot of the flow rate (Q) ofthe medication 12 through a regulator 80 having the physical parametersof the example regulator 80 which was set forth above. In FIG. 12, theflow rate (Q) is plotted in terms of microliters per day (μL/day), as afunction of the driving pressure difference (P) across the regulator 80in mm Hg (millimeters of mercury).

As seen in FIG. 12, at a zero driving pressure difference (P), there isno flow of the medication 12 through the regulator 80. Then, as thedriving pressure difference (P) is increased from zero, the regulator 80exhibits four flow regimes.

That is, as the driving pressure difference (P) is increased from zero,there is a corresponding increase of the flow rate (Q); but there isalso a gradual lessening of the flow rate's (Q's) sensitivity to thedriving pressure difference (P). For example, this is seen on the curve106 at driving pressure differences (P) from about 0.0 mm Hg to about160 mm Hg.

At intermediate driving pressure differences (P) there is a "controlzone" wherein the flow rate (Q) is relatively insensitive changes in thedriving pressure difference (P). For example, this is seen on the curve106 at driving pressure differences (P) from about 160 mm Hg to about250 mm Hg.

Then, although not illustrated in FIG. 12, at driving pressuredifferences (P) higher than the "control zone" the flow rate (Q) mayactually decrease as the driving pressure difference (P) increases.Finally, at very high driving pressure differences (P), the flow rate(Q) may gradually decrease to near zero as the driving pressuredifference (P) of the medication 12 acting on the flexure 98's topsurface 100 drives the flexure 98 down against the regulator seat 90.

It has been discovered that the regulator 80 has a built-in, fail-safecharacteristic, due to its structure, that may provide the user withexceptional protection against catastrophic failure of the flexure 98,when the flexure 98 is subjected to driving pressure differences (P)that are far in excess of the regulator 80's designed driving pressuredifference (P) range.

This fail-safe characteristic exists because, as has been mentioned, atvery high driving pressure differences (P) the medication 12 acting onthe flexure 98's top surface 100 may drive the flexure 98 down againstthe regulator seat 90. When this happens, the regulator seat 90 thenacts as a support for the flexure 98 and prevents its further downwarddeflection; which further deflection might otherwise cause the flexure98 to crack or rupture. As a result, a much higher driving pressuredifference (P) is required to rupture the flexure 98 than wouldotherwise be the case.

The type of response curve 106 shown in FIG. 12 is highly desirable formany applications. This is because the regulator 80 will delivery arelatively constant flow rate (Q) of the medication 12 in its nominal"control zone", despite a substantial range of variations in the drivingpressure difference (P). In addition, if the nominal "control zone"driving pressure difference (P) is exceeded, then the flow rate (Q) ofthe medication 12 will not increase, but may actually decrease; therebyavoiding the possibility of damage which might otherwise be caused ifthe flow regulator 32 permitted more than the desired amount of themedication 12 to flow.

For example, let us assume that a medication delivery device, having asource of medication 12 under pressure, was equipped with a linear flowregulator 80 in order to control the flow rate (Q) of the medication 12from the medication delivery device. As a result, such a medicationdelivery device may be designed for operation in the regulator 80'sabove nominal "control zone" where the flow rate (Q) is relativelyinsensitive to changes in the driving pressure difference (P). This maybe highly desirable, since the patient will receive the medication 12 atthe needed flow rate (Q); despite any variations in the driving pressuredifference (P), such as may be caused by the gradual emptying of themedication delivery device. In addition, if the nominal "control zone"driving pressure difference (P) were to be substantially exceeded, suchas if a medical person accidentally overfilled the medication deliverydevice, then the medication flow rate (Q) will actually fall, therebysignificantly reducing the possibility of injury or death to thepatient, due to an overdose of medication 12, which might otherwiseoccur.

The regulator 80 tends to maintain the flow rate (Q) of the medication12 at a relatively constant value in its above "control zone", despitechanges in the driving pressure difference (P), in the following way. Ifthe driving pressure difference (P) increases, then the flexure 98 willtend to be deflected towards the regulator seat 90 an increased amount,thereby reducing the height of the regulator gap 99. This, in turn,tends to maintain the flow rate (Q) at a relatively constant value,despite the increased driving pressure difference (P). This is becausethe reduced height of the regulator gap 99 will tend to compensate forthe increased driving pressure difference (P) by reducing the flow rate(Q) which would otherwise occur at that increased driving pressuredifference (P).

On the other hand, if the driving pressure difference (P) decreases,then the flexure 98 will tend to be deflected towards the regulator seat90 a decreased amount, thereby increasing the height of the regulatorgap 99. This, in turn, tends to maintain the flow rate (Q) at arelatively constant value, despite the reduced driving pressuredifference (P). This is because the increased height of the regulatorgap 99 will tend to compensate for the reduced driving pressuredifference (P) by increasing the flow rate (Q) which would otherwiseoccur at that reduced driving pressure difference (P).

Lastly, at driving pressure differences (P) above the regulator 80's"control zone", the flow rate (Q) is gradually reduced to zero, as theflexure 98 is driven down closer and closer to the regulator seat 90.

It has been discovered that two quite different strategies may be usedto assist in designing a regulator 80 which has any particular desiredflow regulation characteristics.

The first strategy is one which is empirical in nature. That is, aseries of regulators 80 may be built, and one feature at a time may bevaried, so that the effects of changing that particular feature may bedetermined.

For example, the series flow resistance (R_(s)) of the channel 86 andthe regulator gap 99 may be independently varied by holding constant theregulator gap 99's initial height (when the driving pressure difference(P) is equal to zero); while varying the length of the channel 86 andthe regulator gap 99. Similarly, the regulator gap 99's initial height(when the driving pressure difference (P) is equal to zero) may bevaried by varying the depth and shape of the channel 86; while holdingconstant the length of the channel 86 and the regulator gap 99.

By building and testing a large number of regulators 80; by thenplotting data points for each of them for their various flow rates (Q)versus their driving pressure differences (P); and by then curve-fittingthe plotted data points, it may be possible to generate an empiricalmodel for the performance of the regulator 80 which shows therelationships between key features of the regulator 80 and the operatingbehavior of the regulator 80. These empirical relationships may then beused to interpolate or extrapolate from known design cases to predictthe behavior of a new regulator 80.

The second strategy which may be used to assist in designing a regulator80 which has any particular desired flow regulation characteristics isto develop a mathematical model using numerical methods.

The starting point for formulating the model is that, for any particularregulator 80, the flow of the medication 12 through it may be generallygoverned by the following equation: ##EQU7## where (Q), (P), and (R_(s))are as has been defined above; where (R_(s)) is a direct function of thelength (L) and the wetted perimeter (C) of the channel 86 and theregulator gap 99; where (R_(s)) is an inverse function of thecross-sectional area (A) of the channel 86 and the regulator gap 99; andwhere (R_(s)) is a nonlinear function of the flow rate (Q).

That is, the flow rate (Q) is proportional to the driving pressuredifference (P), and is inversely proportional to the flow resistance(R_(s)) of the channel 86 and the regulator gap 99.

It has been found that accurate prediction of the nonlinear flowresistance (R_(s)) of the channel 86 and the regulator gap 99 mayrequire the consideration of at least the following four factors.

First, the nonlinear flow resistance (R_(s)) of the channel 86 and theregulator gap 99 may be a function of the pressure drop across thelength of the channel 86 and the regulator gap 99, due to their flowresistance (R_(s)). This is because the greater the pressure drop acrossthe length of the channel 86 and the regulator gap 99, the greater thedriving pressure difference (P) across the flexure 98, and the greaterthe amount of the deflection of the flexure 98 towards the regulatorseat 90 (and vice versa). This, in turn, generally decreases the heightof the regulator gap 98; thereby generally increasing the flowresistance (R,) of the channel 86 and the regulator gap 99 (and viceversa). However, such deflection of the flexure 98 is not uniform, sincethe deflected flexure 98 is not flat, but instead assumes a convex, orbowed shape. This results in the nonlinear flow resistance (R_(s)) ofthe channel 86 and the regulator gap 48 being a relatively complexfunction of the pressure drop across the length of the channel 86 andthe regulator gap 99.

Second, the nonlinear flow resistance (R_(s)) of the regulator gap 99may be a function of the viscous shear forces of the medication 12acting on the flexure 98 's bottom surface 101 as the medication 12flows through the length of the regulator gap 99, from the inlet port 88to the outlet port 92. Such viscous shear forces are, in turn, afunction of such things as the viscosity and velocity of the medication12 in the regulator gap 99. Such viscous shear forces are directed alongthe length of the flexure 98's bottom surface 101 and tend to twist ordistort the flexure 98's bottom surface 101 with respect to the flexure98's top surface 100. Such twisting or distorting of the flexure 98tends to vary the size and shape of the regulator gap 99 which, in turn,varies the flow resistance (R_(s)) of the regulator gap 99. This resultsin the nonlinear flow resistance (R_(s)) of the regulator gap 99 being arelatively complex function of the viscous shear forces of themedication 12 acting on the flexure 98.

Third, the nonlinear flow resistance (R_(s)) may be a function of thevelocity of the medication 12 passing through the regulator gap 99. Suchvelocity is, in turn, a function of such factors as the driving pressuredifference (P) across the regulator 80; the height, size, shape andlength of the regulator gap 99; the flow resistance (R_(s)) of thechannel 86 and the regulator gap 99; and the size, shape, length andlocation of the inlet and outlet ports 88, 92.

Because of the Equation of Continuity and Bernoulli's Equation, as thevelocity of the medication 12 through the regulator gap 99 increases,the pressure of the medication 12 within the regulator gap 99 tends todecrease (and vice versa). This is because the Equation of Continuityrequires that the velocity of the medication 12 must increase at arestriction. Thus, since the regulator gap 99 is a restriction (ascompared to the inlet port 94), the velocity of the medication 12 mustincrease as it flows through the regulator gap 99. Bernoulli's equationthen requires that the pressure of the medication 12 in the regulatorgap 99 must fall, due to its increased velocity as it flows through theregulator gap 99.

That is, as the velocity of the medication 12 in the regulator gap 99increases, the pressure of the medication 12 in the regulator gap 99decreases. This increases the amount of the deflection of the flexure98; which, in turn, generally decreases the height of the regulator gap98 and increases the flow resistance (R_(s)) of the channel 86 and theregulator gap 99 (and vice versa).

Fourth, the nonlinear flow resistance (R_(s)) may be a function of theflexure 98's thickness, resiliency, elasticity and stiffness. This isbecause for any given forces acting on the flexure 98, the amount of thedeflection of the flexure 98, and the shape (or radial profile) of thedeflected flexure 98, may be a function of the flexure 98's thickness,resiliency, elasticity and stiffness.

From the forgoing, it is seen that the primary difficulty in developinga mathematical model for the regulator 80 which uses numerical methodsis that the amount of the deflection or bowing of the flexure 98, andthe shape of the flexure 98 as it deflects or bows, are closely coupledand potentially nonlinear in interaction.

However, in developing the mathematical model for the regulator 80, letit now be assumed that the regulator seat 90 has an x,y,z coordinatesystem in which the z axis lies along the longitudinal centerline of theregulator seat 90; in which the x axis is transverse to the z axis,extends left and right from the z axis, and equals zero at the z axis;and in which the y axis is transverse to the x and z axes, measures theheight above the regulator seat 90, and equals zero at the z axis.

In such a coordinate system, the most fundamental flow element consistsof a local fluid slice (dx) wide which spans the gap from the regulatorseat 90 to the flexure 98. If the bowing or deflection of the flexure 98is very slight, then it may be assumed that this local fluid slice hasnegligible shear along its sides and is dominated by viscous drag at itstop and bottom. This is a local fluid slice flow approximation. Withthis assumption, it may be found that the local fluid slice contributionto flow (dQ) is given by: ##EQU8## where μ is the viscosity of themedication 12; and Y_(m) (x) is the height of the local fluid slice.

The bowing or deflection of the flexure 98 towards the regulator seat 90may be dictated by the flexure 98's stiffness. For a pressure difference(P_(s) -p(z)) across the flexure 98, the amount (Y) of the bowing ordeflection of the flexure 98 is given by: ##EQU9## and where (E) isYoung's Modulus; (t) is the thickness of the flexure 98; (w) is thehalf-width of the regulator seat 90; and (X)=x/w. This assumes that theregulator seat 90 has fixed edges, and that there is a guided conditionat the regulator seat 90's center, or at the first point of contact ofthe flexure 98 with the regulator seat 90. A guided condition means thatdY/dx=0 at that point.

If we now solve for the total flow across the local fluid slicecross-section by integrating the above Equation 4, and by incorporatingthe above Equation 5 to provide the height of the local fluid slice,this is found to be: ##EQU10## and where (h) is equal to the height ofthe regulator gap 99.

The dimensionless pressure (P) is a variable that is zero when there isno differential pressure, and is 1.0 when the bowing or deflection ofthe flexure 98 is equal to the height of the regulator gap 99 when thereis a zero driving pressure difference (P) across the flexure 98. Theintegral's value is 0.2781 if P=1. Otherwise, a simple polynomial in Pis obtained. It is clear that the total flow (Q) of the medication 12 isa constant throughout the length of the regulator gap 99. This meansthat for P<1, variables can be separated in the above Equation 6 so thatthe left side is (z), (Q·dz), and the right side is a polynomialfunction of P. This can then be integrated to yield a relationshipbetween the flow rate-channel length product, Q·Z₀, and pressure at agiven axial position: ##EQU11## where (Z₀) is the length of theregulator seat 90. This yields a relation between pressure and totalflow up to the point where P=1. However at this point, since theregulator seat 90 is assumed to be a perfect replica of the bowed ordeflected flexure 98, at a pressure that causes the flexure 98 to touchthe center of the regulator seat 90, the flexure 98 is also in contactwith the entire regulator seat 90, from side to side. Accordingly, theflow rate-channel length product Q·Z₀ is: ##EQU12##

The above model may now be used to predict the performance of the linearflow regulator 80.

Turning again to Figs, 7 and 8, the flexure 98's inlet port edge 94 mayoverlie the channel 86, as seen therein, and thus is not affixed to orrestrained by any portion of the substrate 82. As a result, all of theflexure 98 which is located adjacent to the inlet port 88 (including theinlet port edge 94), is free to fully flex in response to changes in theflow rate (Q) of the medication 12 through the channel 86; as comparedto if the flexure 98's inlet port edge 94 were affixed to or restrainedby any portion of the substrate 82. This may be desirable for at leasttwo reasons. First, it may result in smoother, more predictable,regulation of the flow rate (Q) of the medication 12 by the flexure 98over the regulator 80's designed flow and regulation parameters.

Second, it may also make possible a more compact regulator 80, since thepart of the flexure 98 which is located adjacent to the inlet port 88 isnot rendered wholly or partially inoperative by any portion of thesubstrate 82.

Alternatively, the substrate 82 may be manufactured so that part or allof the flexure 98's inlet port edge 94 may be affixed to or restrainedby some part of the substrate 82. In order to compensate for such astructure, the channel 86 and the flexure 98 may be lengthened so as toprovide the desired overall length of the flexure 98 which iseffectively unrestrained by any portion of the substrate 82.

The channel 86 and the flexure 98 may both have a large length to widthratio (L/W), with "large" being defined in this context to be a L/W inthe range of about 5:1 to 1000:1. Preferably, the L/W may be about 20:1.A large L/W may be desirable because it may allow the linear flowregulator 80 to have a more robust flexure 98, since the membrane 84'sregulator function is distributed over a longer length, as compared to aregulator 80 with a flow channel 86 and a flexure 98 having a small L/Wratio, such as 1:1.

A more robust flexure 98 may be desirable since it may be more durable,it may be less likely to rupture due to undesired operatingoverpressures, it may be easier to manufacture, and it may be easier tohandle during the assembly of the flow regulator 80, as compared to aless robust flexure 84.

A channel 86 and a flexure 98 having a large L/W ratio also allows theuse of a channel 86 and a regulator gap 99 having a largercross-sectional area, for any particular designed flow and regulationparameters, as compared to a channel 86 and a flexure 98 having a smallL/W ratio. This is because as the channel 86 becomes longer, its fluidresistance (R_(s)) becomes greater. Thus, for any particular desiredoperating pressure, in order to obtain a particular desired flow rate(Q), the cross sectional area of the channel 86 and the regulator gap 99will have to be made larger, as the channel 86 and the flexure 98 becomelonger, in order to compensate for the otherwise increased fluidresistance (R_(s)) of the elongated channel 86 and the regulator gap 99.

Such an elongated channel 86 and regulator gap 99, having a largercross-sectional area for a particular desired operating pressure andflow rate, may be desirable because their larger cross-sectional areamay be less likely to foul due to contaminants in the medication 12, dueto corrosion of the channel 86, the regulator seat 90, and the flexure98.

From the disclosures in this document, it is possible to selectivelydesign a linear flow regulator 80 for any particular desired flowregulation characteristics or driving pressure difference (P). This maybe done by selectively adjusting one or more of the pertinentparameters, such as: (a) the number, size, shape, length and location ofthe inlet port 88 and the outlet port 92; (b) the number, size,cross-sectional configuration, and length of the channel 86 and theregulator gap 99; and (c) the length, thickness, resiliency, elasticityand stiffness of the flexure 98.

MICROMACHINED LINEAR FLOW REGULATOR 80 HAVING A CONTOURED REGULATOR SEAT90 (FIGS. 7-12): MANUFACTURE

The substrate 82 may be made from any suitable strong, durable materialwhich is compatible with the medication 12, and in which the channel 86and the outlet port 54 may be manufactured in any suitable way, such asby using any suitable etching, molding, stamping and machining process.Such a machining process may include the use of physical tools, such asa drill; the use of electromagnetic energy, such as a laser; and the useof a water jet.

The membrane 84 may be made from any suitable strong, durable, flexible,material which is compatible with the medication 12. The membrane 84 mayalso be elastic.

If the regulator 80 is intended to regulate a medication 12 which is tobe supplied to a human or an animal, then any part of the regulator 80which is exposed to the medication 12 should be made from, and assembledor bonded with, non-toxic materials. Alternatively, any toxic materialwhich is used to manufacture the regulator 80, and which is exposed tothe medication 12 during use of the regulator 80, may be provided withany suitable non-toxic coating which is compatible with the medication12.

Suitable materials for the substrate 82 and the membrane 84 may bemetals (such as titanium), glasses, ceramics, plastics, polymers (suchas polyimides), elements (such as silicon), various chemical compounds(such as sapphire, and mica), and various composite materials.

The substrate 82 and the membrane 84 may be assembled together in anysuitable leak-proof way. Alternatively, the substrate 82 and themembrane 84 may be bonded together in any suitable leak-proof way, suchas by anodically bonding them together; such as by fusing them together(as by the use of heat or ultrasonic welding); and such as by using anysuitable bonding materials, such as adhesive, glue, epoxy, glass solder,and metal solder.

Anodically bonding the substrate 82 to the membrane 84 may be preferablefor at least four reasons. First, anodic bonding is relatively, quick,easy and inexpensive. Second, an anodic bond provides a stable,leak-proof bond. Third, since an anodic bond is an interfacial effect,there is no build-up of material at the bond; and the bond hasessentially a zero thickness, which desirably creates no essentially nospacing between the substrate 82 and the membrane 84. As a result, ananodic bond does not interfere with the desired height or shape of theregulator gap 99.

Fourth, an anodic bond may be preferable since it eliminates the needfor any separate bonding materials, which might otherwise clog or reducethe size of the inlet port 88, the channel 86, the regulator gap 99, andthe outlet port 92; or which might lead to corrosion of the jointbetween the substrate 82 and the membrane 84.

One example of how the linear flow regulator 80 may be manufactured willnow be given.

The starting point may be a 76.2 mm diameter wafer of Corning 7740 Pyrexglass, which will form the regulator 80's substrate 82.

The channel 86 and its regulator seat 90 may then be formed in thesubstrate 82 in any suitable way. One suitable way may be to first etcha generally rectangular channel into the substrate 82, wherein therectangular channel has a length and a depth about equal to the lengthand the depth of the desired channel 86 and regulator seat 90. Therectangular channel may be etched into the substrate 82 in any suitableway, such as by using a process which is the same as, or at leastsimilar to, that used to etch the radial flow regulator 32's inletchannels 38 into its substrate 34.

After the rectangular channel has been etched, the regulator 80's outletport 92 may be formed. The structure, operation, theory and manufactureof the linear flow regulator 80's outlet port 92 is the same as, or atleast similar to, that of the radial flow regulator 32's outlet port 54,except for those differences, if any, which will be made apparent by anexamination of all of the Figures and disclosures in this document.

After the outlet port 92 has been formed, a nominal layer of one or morecorrosion-resistant substances may be deposited onto the top surface ofthe glass wafer in any suitable way. As a result, the channel 86, theregulator seat 90, and the outlet port 92 will have been coated with alayer of the corrosion-resistant substance(s). The structure, operation,theory and manufacture of such a layer of one or morecorrosion-resistant substances for the linear flow regulator 80 is thesame as, or at least similar to, that of the radial flow regulator 32'slayer of one or more corrosion-resistant substances, except for thosedifferences, if any, which will be made apparent by an examination ofall of the Figures and disclosures in this document.

After the channel 86 and the regulator seat 90 have been etched, andafter any desired layer of corrosion-resistant substance(s) has beenapplied to etched portions of the glass wafer, the photoresist andchrome which remain on the unetched portions of the glass wafer may beremoved by any suitable means, such as by using standard lift-offtechniques.

At this point, certain work on the manufacture of the membrane 84 may bedone before the desired channel 86 and regulator seat 90 may becompleted. Manufacturing the membrane 84 and bonding it to the glasswafer (which is the substrate 82) may be done in any suitable way. Thestructure, operation, theory and manufacture of the linear flowregulator 80's membrane 84 and the bonding of the membrane 84 to itssubstrate 82 to form a silicon/glass sandwich is the same as, or atleast similar to, the manufacture of the radial flow regulator 32'smembrane 36, and the bonding of the membrane 36 to its substrate 34 toform a silicon/glass sandwich, except for those differences, which willbe made apparent by an examination of all of the all of the Figures anddisclosures in this document.

Some of those differences will now be addressed. It may be recalled thatthe starting point for the regulator 80's membrane 84 may be a primesilicon wafer having a boron-doped epitaxial silicon layer which hasbeen deposited onto one of its surfaces. Since the boron doped layerwill ultimately form the regulator 80's membrane 84, the boron-dopedlayer's thickness will depend on the desired thickness of the membrane84. The boron-doped layer has a dramatic etch-resistance to siliconetchants based on ethylene diamine; but is easily etched by isotropicetchants. The isotropic etchants will also easily etch the non-dopedlayer of the silicon wafer.

Accordingly, the first step in manufacturing the regulator 80's membrane84 is to first clean the silicon wafer; apply a thin chromemetallization layer to both of the wafer's surfaces; and then apply anddry a thin layer of any suitable photoresist on top of the chrome layer.

An image of the inlet port 88 may then be exposed onto the photoresiston the silicon wafer's boron-doped layer, and then developed; afterwhich the silicon wafer may be cleaned and dried.

As a result of the forgoing procedure, the chrome layer over theboron-doped layer will now bear an image, unprotected by thephotoresist, of the inlet port 88. The unprotected portion of the chromelayer may then be etched away; resulting in an image of the inlet port88 having been formed on the boron-doped layer, which image isunprotected by the layers of photoresist and chrome which cover the restof the silicon wafer. The image of the inlet port 88 may then be etchedinto the boron-doped layer to a depth which is at least slightly greaterthan the thickness of boron-doped layer in any suitable way, such as byusing an isotropic etchant. The photoresist and the chrome layers maythen be removed from the silicon wafer, which may then be cleaned anddried.

The silicon and glass wafers may then be aligned, so that the etchedimage of the inlet port 88 in the boron-doped layer is in properregistry with the etched image of the channel 86 in the glass wafer. Theetched surfaces of the silicon and glass wafers may then be anodicallybonded together; after which the non-doped layer of the silicon wafermay then be etched and ground to produce the desired membrane 84, withthe desired inlet port 88. The desired inlet port 88 is automaticallyformed during the etching and grinding of the non-doped layer of thesilicon wafer because the isotropic etchant had previously completelyetched away the image of the inlet port 88 in the boron-doped layer ofthe silicon wafer; so that when the non-doped layer of the silicon waferis etched and ground away, the inlet port 88 is automatically formed.

The desired contour may be imparted to the channel 86's regulator Seat90 in any suitable way. One suitable way may be to use a pressureforming method, in which the substrate 82 may first be placed into aforming device which restrains the substrate 82's bottom surface 104 andits lateral edges. A flat stencil having a cutout whose length and widthcorresponds to that of the desired channel 86 may be provided; themembrane 84 may be tightly sandwiched between the stencil and thesubstrate 82; and at least the substrate 82 may be heated to an elevatedprocess temperature at which the substrate 82 is softened. For example,the elevated process temperature for a Pyrex glass substrate may beabout 600° C.

The portion of the membrane 84 which is exposed through the stencil(i.e., the flexure 98), may then exposed to a pressure about equal tothe regulator 80's maximum designed driving pressure difference (P),thereby deflecting the flexure 98 down into the softened substrate 82and forming the channel 86's contoured regulator seat 90. For example,for a Pyrex glass substrate which is heated to about 600° C., thepressure may be about 100 pounds per square inch (psi). The rectangularchannel mentioned above, which was etched into the substrate 82, may aidin the formation of the desired contoured regulator seat 90 since allthe deflected flexure 98 needs to do is to mold the rectangularchannel's sides and bottom into the desired contour. The forming devicefor the substrate 82 may have a relief hole which permits the exit ofany excess substrate 82 material which is displaced by the deflectedmembrane 84. Alternatively, the rectangular channel mentioned above maybe dispensed with, and the flexure 98 may be deflected with pressuredown into the softened substrate 82 to form the contoured regulator seat90.

The desired pressure may then be maintained on the flexure 98 while thesubstrate 82 is cooled and hardened, thereby forming the substrate 82'schannel 86 with the desired contour in its regulator seat 90. Thepressure may then be released, allowing the elastic flexure 98 to returnto its undeflected configuration. The stencil, the forming device andany undesired displaced substrate 82 material may then be removed.

Although the use of a heat softened substrate 82 was described above,the contoured regulator seat 90 may be pressure formed into thesubstrate 82 in any other suitable way. For example, the substrate 82may be selected to be made from a material, such as an epoxy, a ceramicmaterial or a solvent-softened material, which is soft at roomtemperature, and which is then hardened after the flexure 98 isdeflected down into it by a chemical reaction, by the application ofheat, or by the evaporation of the solvent, respectively.

Another way to form the contoured regulator seat 90 may be tomicromachine the desired contour into the substrate 82 by use of a laserbeam. Such a laser beam may be regulated, by any suitable means, to havean intensity gradient similar to that of the desired contour of thechannel 86's regulator seat 90, such as by projecting the laser beamthrough one or more suitable lenses and/or gradient filters.

Another way of using a laser beam to micromachine the desired contourinto the substrate 82 may be to project the laser beam through a mask togive at least a portion of the laser beam a cross-sectionalconfiguration which is similar to that the desired contour of theregulator seat 90.

The manufacture of only one linear flow regulator 80 was describedabove. However, it will be appreciated that on any pair of glass andsilicon wafers numerous regulators 80 could be manufacturedsimultaneously in a manner similar to that described above. If such isthe case, an array of substrates 82 may be simultaneously etched in theglass wafer before the silicon and glass wafers are aligned and bondedtogether. Then, all of the membranes 36, and their inlet ports 88 may beformed simultaneously. The silicon/glass sandwich may then be divided byany suitable means (such as dicing) into individual chips, each chipbearing at least one linear flow regulator 80.

One of the advantages of using the etching, anodic bonding, and pressureforming process which was described in detail above is that such aprocess enables high quality, very reliable linear flow regulators 80 tobe mass produced in great numbers at a cost so low that the regulator 80may be considered to be disposable. In addition, it should also be notedthat the regulator 80 is stunning in its simplicity since it may have asfew as only two parts (the substrate 82 and the membrane 84); and sinceit may have only one moving part (the membrane 84's flexure 98).Further, the cost of the regulator 80 may held to a very low levelbecause the raw materials from which the regulator 80 may be made may bevery inexpensive, such as glass and silicon.

MICROMACHINED LINEAR FLOW REGULATOR 110 HAVING A NON-CONTOURED REGULATORSEAT 90 (FIGS. 13-15): STRUCTURE

The linear flow regulator 110 which is illustrated in FIGS. 13-14 is thesame as, or at least similar to, the linear flow regulators 80 of FIGS.7-11 in its structure, except for those differences, if any, which willbe made apparent by an examination of all of the Figures and disclosuresin this document. Accordingly, the respective parts of the linear flowregulator 110 of FIGS. 13-14 has been given the same reference numeralsas the corresponding parts of the linear flow regulators 80 of FIGS.7-11, for clarity and simplicity.

As seen in FIGS. 13-14, the linear flow regulator 110 has a pair ofoutlet ports 92; and a channel 86 having a pair of sides 112 which areat right angles to the non-contoured regulator seat 90.

As used herein, the term "non-contoured" means that the regulator seat90 does not approximate, or duplicate, the contoured shape that theflexure 98 would assume if the flexure 98 were entirely unrestrained byany part of the substrate 82 when the linear flow regulator 110 issubjected to the regulator 110's maximum designed driving pressuredifference (P) of the medication 12 between the regulator 110's inletport 88 and outlet port 92.

It should be understood that FIGS. 13-14 illustrate only one example ofa non-contoured regulator seat 90, i.e., a flat non-contoured regulatorseat 90. Naturally, the non-contoured regulator seat 90 could have anyof a variety of other configurations, shapes, or forms.

By way of example, the linear flow regulator 110's substrate 82 may bemanufactured from 7740 Pyrex glass, and may have a thickness of about0.5 mm. The channel 86 and the regulator seat 90 may have a length ofabout 1.0 cm, and may have a maximum width of about 508 microns. Theregulator gap 99 may have a maximum height of about 4.2 microns (whenthe driving pressure difference (P) is equal to zero). Each outlet port92 may have a minimum diameter of about 100 microns, and may have alength of about 496 microns. The membrane 84 may be manufactured fromsilicon, and may have a thickness of about 9.0 microns. The inlet port88 may have a width of about 508 microns, and a length of about 500microns. The flow characteristics of this example linear flow regulator110 are illustrated in FIG. 15, which will be discussed below.

MICROMACHINED LINEAR FLOW REGULATOR 110 HAVING A NON-CONTOURED REGULATORSEAT 90 (FIGS. 13-15): OPERATION AND THEORY

The linear flow regulator 110 which is illustrated in FIGS. 13-14 is thesame as, or at least similar to, the linear flow regulators 80 of FIGS.7-11 in its operation and theory, except for those differences, if any,which will be made apparent by an examination of all of the Figures anddisclosures in this document.

During operation, as a driving pressure difference (P) is applied acrossthe regulator 110, such as by pressurizing the source of the medication12 with respect to the regulator 110's outlet port 92 by any suitablemeans, the medication 12 will pass sequentially through the regulator110's inlet port 88, regulator gap 99, and outlet port 92.

Referring now to FIG. 15, the flow rate (Q) of the medication 12 throughthe regulator 110 is plotted in terms of microliters per day (μL/day),as a function of the driving pressure difference (P) across theregulator 110 in mm Hg. The regulator curve 114 is a plot of atheoretical mathematical model of the flow rate (Q) of the medication 12for a regulator 110 having the physical parameters of the exampleregulator 110 which was set forth above. The theoretical mathematicalmodel will be discussed below. The seven square data points 116 seen inFIG. 15 are for the measured flow rates (Q) of an actual flow regulator110 having the physical parameters of the example regulator 110 whichwas set forth above. As seen, the theoretical model does quite well inpredicting the performance of the flow regulator 110.

FIG. 15 reveals that, at a zero driving pressure difference (P), thereis no flow of the medication 12 through the regulator 110. Then, as thedriving pressure difference (P) is increased from zero, the regulator110 exhibits two main flow regimes.

That is, as the driving pressure difference (P) is increased from zero,there is a corresponding increase of the flow rate (Q); but there isalso a gradual lessening of the flow rate's (Q's) sensitivity to thedriving pressure difference (P). For example, this is seen on the curve114 at driving pressure differences (P) from about 0.0 mm Hg to about120 mm Hg.

Then, at higher pressure differences (P), there is a "control zone"wherein the flow rate (Q) is relatively linear function of changes inthe driving pressure difference (P), and the sensitivity of theregulator 110 to changes in the driving pressure difference (P) isreduced by about 45%, as compared to a device having no flow regulationproperties at all.

This behavior of the flow regulator 110 during operation is due to thefact that, as the driving pressure difference (P) across the regulator110 is increased, the flexure 98 tends to be deflected towards theregulator seat 90 an increased amount, thereby reducing the height ofthe regulator gap 99. This, in turn, tends to maintain the flow rate (Q)at a relatively constant value, despite the increased driving pressuredifference (P). This is because the reduced height of the regulator gap99 will tend to compensate for the increased driving pressure difference(P) by reducing the flow rate (Q) which would otherwise occur at thatincreased driving pressure difference (P).

On the other hand, if the driving pressure difference (P) decreases,then the flexure 98 will tend to be deflected towards the regulator seat90 a decreased amount, thereby increasing the height of the regulatorgap 99. This, in turn, tends to maintain the flow rate (Q) at arelatively constant value, despite the reduced driving pressuredifference (P). This is because the increased height of the regulatorgap 99 will tend to compensate for the reduced driving pressuredifference (P) by increasing the flow rate (Q) which would otherwiseoccur at that reduced driving pressure difference (P).

However, as seen in FIG. 13, even when the driving pressure difference(P) has been increased to the point where the flexure 98 is deflected somuch that it starts to contact the regulator seat 90, the medication 12will still be permitted to flow through the two side channels 118 whichare formed between the deflected flexure 98, the regulator seat 90'sside portions 120, and the channel 98' side walls 112.

Lastly, as the driving pressure difference (P) is increased stillfurther, the flexure 98 will be flattened against the regulator seat 90an increased amount, thereby gradually decreasing the size of the sidechannels 118 (and vice versa).

In order to assist in designing the regulator 110 to have any particulardesired regulator curve 114, either an empirical strategy or amathematical model may have to be employed.

The starting point for the mathematical model is the mathematical modelwhich was set forth above regarding the regulators 80. It will berecalled that the above equation 7 yielded a relation between thedriving pressure difference (P) and the total flow rate (Q) of themedication 12 up to the point P=1, the dimensionless pressure at whichthe flexure 98 first contacts the regulator seat 90.

However, beyond that pressure the flexure 98 will spread laterallyacross the regulator seat 90; and the first point of contact between theflexure 98 and the regulator seat 90 will expand and move along the zaxis towards the inlet port 88.

In this mode of operation, the dimensionless pressure (P) still cannotexceed 1.0 since the depth of the channel 86 is fixed. Instead, as hasbeen mentioned, two parallel side channels 118 are formed, each having asize which is a function of the driving pressure difference (P). Thatis, as the driving pressure difference (P) increases, the size of theside channels 118 decreases, (and vice versa).

For a channel 86 having a length Z₀, the point of first contact betweenthe flexure 98 and the regulator seat 90 is some fraction of thatlength, i.e., n·Z₀. Since P=1 at each local fluid slice in the two sidechannels 118, the effective width of each of the side channels 118 is:

    W.sub.e =W/p.sup.0.25

where P>1.

From the above Equation 6, for the boundary condition P=1, the followingdifferential equation for pressure drop can be obtained: ##EQU13## where(Q₀) is the flow when the contact between the flexure 98 and theregulator seat 90 is at z=Z₀. That is, when P=1 is the above Equation 7.Upon separation of variables, and some algebraic manipulation, asurprisingly simple relationship for flow versus pressure is found inthe mode where there is contact between the flexure 98 and the regulatorseat 90:

    Q=Q.sub.0 [1+0.4271(P.sup.1.25 -1)]

where P>1.

The above model may now be used to predict the performance of the linearflow regulator 110.

From the disclosures in this document, it is possible to selectivelydesign a linear flow regulator 110 for any particular desired flowregulation characteristics or driving pressure difference (P). This maybe done by selectively adjusting one or more of the pertinentparameters, such as: (a) the number, size, shape, length and location ofthe inlet port 88 and the outlet port 92; (b) the number, size,cross-sectional configuration, and length of the channel 86 and theregulator gap 99; (c) the length and shape of the regulator seat 90; (d)the length and shape of the side channels 118; and (e) the length,thickness, resiliency, elasticity and stiffness of the flexure 98.

MICROMACHINED LINEAR FLOW REGULATOR 110 HAVING A NON-CONTOURED REGULATORSEAT 90 (FIGS. 13-15): MANUFACTURE

The manufacture of the linear flow regulator 110 of FIGS. 13-14 may bethe same as, or at least similar to, the linear flow regulators 80 ofFIGS. 7-11, except for those differences, if any, which will be madeapparent by an examination of all of the Figures and disclosures in thisdocument.

Since the regulator 110 has a non-contoured regulator seat 90, the stepsrelating to pressure forming the regulator 80's contoured regulator seat90 may be eliminated. Instead, the rectangular channel is etched intothe substrate 82 so that the rectangular channel has a length, width anddepth which are equal to that of the desired channel 86. In other words,the etched rectangular channel becomes the desired channel 86, and theetched rectangular channel's bottom forms the non-contoured regulatorseat 90; with no further work being needed in order to form the desiredchannel 86 and the non-contoured regulator seat 90.

Another way to form the channel 86 and the non-contoured regulator seat90 may be to use a laser beam or a water jet.

MICROMACHINED DIAPHRAGM PUMP 130 HAVING INTEGRAL VALVING AND A CENTRALLYLOCATED INLET PORT (FIGS. 16-17): STRUCTURE

The first embodiment of the micromachined diaphragm pump 130 for themedication 12 is illustrated in FIGS. 16-17. The pump 130 may have fivebasic structures, namely a substrate 132; a one-way inlet valve 134; amembrane 136; a one-way outlet valve 137; and a piezoelectric motor 138.

The substrate 132 may have a circular pumping cavity 140 with an inletport 142; a circular outlet valve cavity 144 with an outlet port 146;and a channel 147 which connects the pumping cavity 140 and the outletvalve cavity 144. Although the cavities 140, 144 are illustrated asbeing circular, they may have any other suitable'size and shape.Although only one, rectangular channel 147 is illustrated, there may bemore channels 147, and each channel 147 may have any other suitable sizeand shape. Although the inlet and outlet ports 142, 146 are illustratedas having a venturi-like shape for better fluid flow therethrough, theymay have any other suitable size and shape.

The membrane 136 may have a mounting portion 139, which may be mountedto a respective portion of the substrate 132's top surface 158; anoutlet valve flexure 157, which overlies the outlet cavity 144; and apumping flexure 160, which overlies the pumping cavity 140.

Within the pumping cavity 140 may be twelve flexure supports 148; whichmay prevent the pumping flexure 160 from being broken in the event thepumping flexure 160 is inadvertently forced downwardly towards thepumping cavity 140's bottom 150. The flexure supports 148 may also serveto prevent the pumping flexure 160 from being deflected downwardly morethan a predetermined amount by the motor 138 during operation of thepump 130. Although the twelve flexure supports 148 are illustrated asbeing in the form of radial spines in FIGS. 16-17, there may be fewer ormore flexure supports 148, and each flexure support 148 may have anyother suitable size and shape, such as the cylindrical pin shapedflexure supports 148 which are illustrated in FIGS. 18-19.

It has been discovered that using relatively small cylindrical pinshaped flexure supports 148 (FIGS. 18-19), instead of relatively largeradial spine type flexure supports 148 (FIGS. 16-17), may beadvantageous for at least four reasons. First, they may have less flowresistance to the medication 12 being pumped by the pump 130. Second,they may have less adverse impact on the priming of the pumping cavity140. Third, they may have less propensity to undesirably trap bubbleswithin the pumping cavity 140. Fourth, they may have less of an adverseimpact on the ability of the medication 12 to sweep any bubbles out ofthe pumping cavity 140 during operation of the pump 130.

The one-way inlet valve 134 may comprise a circular inlet valve seat152; an inlet cavity 153; an inlet valve flexure 154; and a pair ofbosses 156, to which the ends of the inlet valve flexure 154 may bebonded. The tops of the inlet valve seat 152 and the bosses 156 may beflat and coplanar, so that the inlet valve flexure 154 may lay flatacross the top of the inlet valve seat 152, as seen in FIG. 16, when nomedication 12 is entering the pumping cavity 140 through its inlet port142. The inlet cavity 153 may be used to define a clean outer perimeterfor the inlet port 142, particularly if the inlet port 142 is drilledwith a laser. However, the inlet cavity 153 may be eliminated, and theinlet port 142 may be extended upwardly so that it communicates directlywith the inlet valve seat 154's top surface. Alternatively, the inletport 142 may be eliminated, and the inlet cavity 153 may be extendeddownwardly so that it communicates directly with the substrate 132'sbottom surface.

The one-way outlet valve 137 may comprise a circular outlet valve seat155; an outlet cavity 159; and the outlet valve flexure 157. The top ofthe outlet valve seat 155 and the substrate 132's top surface 158 may beflat and coplanar, so that the outlet valve flexure 157 lies flat acrossthe top of the outlet valve seat 152, as seen in FIG. 16, when nomedication 12 is exiting the outlet valve cavity 144 through its outletport 146. The outlet cavity 159 may be used to define a clean outerperimeter for the outlet port 146, particularly if the outlet port 146is drilled with a laser. However, the outlet cavity 159 may beeliminated, and the outlet port 146 may be extended upwardly so that itcommunicates directly with the outlet valve seat 155's top surface.Alternatively, the outlet port 146 may be eliminated, and the outletcavity 159 may be extended downwardly so that it communicates directlywith the substrate 132's bottom surface.

From the foregoing, it is seen that the membrane 136 may serve triplefunctions; namely, its pumping flexure 160 may serve as the diaphragmfor the pumping cavity 140; its outlet valve flexure 157 may serve asthe diaphragm for the outlet valve 137; and its mounting portion 139 mayseal the membrane 136 to the substrate 132's top surface 158, to preventleakage from the pumping cavity 140, the outlet valve cavity 144, andthe channel 147.

Although the inlet and outlet valve seats 152, 155 are illustrated asbeing circular, they each may have any other suitable size and shape.Although one particular form of one-way inlet and outlet valves 134, 137are illustrated in FIGS. 16-17, the pump 130's one-way inlet and outletvalves 134, 137 may be any other suitable one-way valve, such as theone-way valves which are disclosed in this document.

The piezoelectric motor 138 may comprise a sandwich formed by bondingtogether a piezoelectric disk 162 and a conductive cover disk 164. Thesandwich may then, in turn, be bonded to the pumping flexure 160.

Alternatively, the cover disk 164 may be eliminated, and thepiezoelectric disk 162 may be firmly bonded to the pumping flexure 160'stop surface in any suitable way, such as by using a layer 168 of a hardbonding material, such as an epoxy. In such an event, the pumpingflexure 160 would assume the role served by the cover disk 164. However,such a construction is not preferred since such a layer 168 of hardbonding material between the piezoelectric disk 162 and the pumpingflexure 160 may lead to undesirable distortions of the pumping flexure160 over the operating temperature range; and may lead to limiting thedisplacement of the pumping flexure 160 (for any given power input), dueto radial shear between the piezoelectric disk 162 and the pumpingflexure 136.

Any suitable source of electrical power may be supplied to thepiezoelectric motor 138 through a pair of wires 170, 172. The wire 170may be electrically connected to the motor 138's cover disk 164 in anysuitable way, and the wire 172 may be electrically connected to thebottom of the piezoelectric disk 162 in any suitable way.

By way of example, the diaphragm pump 130 may have a weight of about 0.6grams; and may have the following physical parameters. The substrate 132may be a square having sides about 1.30 cm long, and a thickness ofabout 0.5 mm. The membrane 136 may have a thickness of about 25 microns.The inlet valve flexure may have a thickness of about 9 microns, a widthof about 1940 microns, and a length of about 2900 microns. The pumpingcavity 140 may have a diameter of about 1.07 cm, and the outlet valvecavity 144 may have a diameter of about 3.4 mm. The cavities 140, 144and the channel 147 may each have a depth of about 25 microns. Thechannel 147 may have a width of about 0.5 mm, and a length of about 1.0mm. The inlet and outlet ports may have a minimum diameter of about50-100 microns. The flexure supports 148 and the outlet valve seat 154may have a height of about 25 microns. The inlet valve seat 152 and theinlet valve flexure bosses 156 may have a height of about 9 microns. Thepiezoelectric motor 138 may act as about a 0.02 μF capacitor; and itsdisks 162, 164 may have a thickness of about 0.15 mm, and a diameter ofabout 1.1 cm. The bonding material 168, which bonds the disk 162 to thepumping flexure 160's top surface may have a thickness of about 50microns; and the wires 170, 172 may have a diameter of about 50 microns.This example pump 130 may deliver about 0.1 to 1.0 microliters of themedication 12 per pumping cycle; and operate at a frequency of fromabout 0.0 to about 25.0 pumping cycles per second.

Naturally, any of the forgoing physical parameters of the diaphragm pump130 may be varied, in order to provide a pump 130 having the particularsize, pumping and operating characteristics which may be desired.

As will be appreciated from all of the disclosures in this document,since the pump 130 may have an extremely small size, an extremely lowweight, a very small number of parts, and a very small electrical energyconsumption, the pump 130 has numerous advantages over a pump 130 whichis physically much larger, much heavier, more complex, or a much largerconsumer of electrical energy. For example, the pump 130 of the presentinvention may be ideal for use as part of a miniaturized medicationdelivery device which is to be implanted in a human or animal fordelivery of flow rates of the medication 12 as low as about 0.05microliters per pumping cycle--flow rates which are so low that they maybe impossible for a physically larger pump of a different design toreliably and accurately deliver.

MICROMACHINED DIAPHRAGM PUMP 130 HAVING INTEGRAL VALVING AND A CENTRALLYLOCATED INLET PORT (FIGS. 16-17): OPERATION AND THEORY

The diaphragm pump 130 may be installed in its intended location of usein any suitable way. Any suitable medication supply means may be used toconnect the pump 130's inlet port 142 to a source of the medication 12;and any suitable medication delivery means may be used to connect thepump 130's outlet port 146 to whatever person, animal or thing is toreceive the medication 12 from the outlet port 146.

During operation, when any suitable source of electrical power isapplied to the piezoelectric motor 138's wires 170, 172 (such as 100volts D.C., with the voltage being applied to the wires 170, 172 in thesame polarity as the original ferroelectric polarization of thepiezoelectric disk 162), the piezoelectric disk 162 may tend to contractradially. The amount of such contraction is a function of the voltageapplied to the wires 170, 172, with the piezoelectric disk 162 tendingto contract more as the voltage is increased (and vice versa).

However, since the radial contraction of the disk 162's top surface isrestricted by its bonded cover disk 164, the piezoelectric motor 138tends to assume a cupped shape, with the motor 138's center being raisedup above the substrate 132's top surface 158 by about 25 microns, asseen in FIG. 16. In turn, since the motor 138 is bonded to the pumpingflexure 160's top surface, this cupping action of the motor 138 causesthe pumping flexure 160 to also tend to assume a cupped shape, with thecenter of the pumping flexure 160 also being raised up above thesubstrate 132's top surface 158 by about 25 microns, as is further seenin FIG. 16.

It has been discovered that selecting the diameter of the motor 138 tobe at least slightly larger than the diameter of the pumping cavity 140and the pumping flexure 160 may be preferable for at least two reasons.First, if the motor 138 is larger than the pumping flexure 160, then themotor 138 may protect the entire pumping flexure 160 from physicaldamage. Second, if the motor 138 is larger than the pumping cavity 140,then the peripheral edge of the motor 138 may rest on a portion of themembrane 136 which is directly supported by the substrate 132. Thus,when electrical power is applied to the motor 138's wires 170, 172, theperipheral edge of the motor 138 may act as a circular, circumferentialfulcrum as the motor 138 assumes its cupped shape. However, the motor138 may have a diameter which is less than the diameter of the pumpingcavity 140 and the pumping flexure 160.

When the motor 138 and the pumping flexure 160 assume their above cuppedshapes, the pressure of the medication 12 within the pumping cavity 140,channel 147 and outlet valve cavity 144 is reduced. The negativepressure does two things simultaneously. First, the negative pressurecauses the inlet valve flexure 154 to bow upwardly; thereby unseatingthe inlet valve flexure 154 from the inlet valve seat 152, and drawingthe medication 12 into the pumping cavity 140. Second, the negativepressure causes the outlet valve flexure 157 to be pulled downwardly;thereby seating the outlet valve flexure 157 against the outlet valveseat 155, and preventing any medication 12 in the pump 130's outlet port146 from flowing into the outlet valve cavity 144.

On the other hand, if the source of electrical power to the motor 138'swires 170, 172 is reduced, or interrupted, the piezoelectric disk 162will reduce, or cease, its radial contraction, since the amount of theradial contraction of the disk 162 is a function of the voltage appliedto the wires 170, 172. As a result, the piezoelectric motor 138 and thepumping flexure 160 will automatically tend to return to their original,flat configurations, due to their resiliency and elasticity. As thishappens, pressure of the medication 12 within the pumping cavity 140,the channel 147 and the outlet valve cavity 144 is increased.

This increase in the pressure of the medication 12 does two things.First, it forces the inlet valve flexure 154 downwardly; thereby seatingthe flexure 154 against the inlet valve seat 152, and preventing themedication 12 from flowing back out of the inlet port 142. Second, thisincrease in the pressure of the medication 12 causes the outlet valveflexure 157 to bow upwardly; thereby unseating the outlet valve flexure157 from the outlet port's valve seat 152, and permitting the medication12 to flow out of the pump 130's outlet port 146.

For the example pump 130, whose physical parameters were set forthabove, the forgoing complete pumping cycle of the pump 130 correspondsto an output of from about 0.1 to about 1.0 microliters of medication 12from the pump 130's outlet port 146.

From the forgoing, it will now be appreciated that the output of themedication 12 from the pump 130 for each of its pumping cycles may beselectively varied by controlling the input voltage which is applied tothe motor 138's wires 170, 172. That is, within certain limits, whichmay be determined by the sizing of the pump 130 and the materials usedin the pump 130, the amount of the displacement of the pumping flexure160 is a function of the amount of the input voltage. In other words, asthe input voltage is increased, the displacement of the membrane 138'spumping flexure 160 also increases, thereby increasing the output of themedication 12 from the pump 130 for each of its pumping cycles (and viceversa).

The total output from the pump 130 is governed by the displacement ofthe pumping flexure 160 during each of the pump 130's pumping cycles;and by the frequency of the input voltage to the motor 138's input wires170, 172 which, in turn, governs the frequency at which the pump 130 iscycled. In other words, one complete cycle of the input voltage willresult in one complete pumping cycle of the pump 130. For example, theexample pump 130, whose physical parameters were set forth above, may becycled as rapidly as about 25 times per second, although its efficiencymay peak at lower cycle rates, such as about once per second. If theexample pump 130 is cycled once per second, its total output of themedication 12 from its outlet port 146 will be about 6.0 to about 60.0microliters of medication 12 per minute, or about 8.64 to about 86.4 ccper day.

Alternatively, instead of merely reducing or interrupting the electricalpower to the motor 138's wires 170, 172, during the pump 130's abovepumping cycle, the polarity of the voltage applied to the wires may bereversed during the pump 130's above pumping cycle. During such bipolaroperation of the pump 130, instead of the centers of the motor 138 andthe pumping flexure 160 merely tending to automatically return to theiroriginal, flat configurations, they would also tend to be driven to bebowed or cupped downwardly towards the pumping chamber 140's bottom 150.

Thus, the direction of the displacement of the membrane 138's pumpingflexure 160 will be a function of the polarity of the input voltage,while the amount of such displacement will be a function of the amountof the input voltage.

From the forgoing, it will now be appreciated that if the motor 138 issupplied with a D.C. voltage whose polarity is periodically reversed,and if the height of the flexure supports 148, the height of the inletvalve 134, and the depth of the pumping cavity 140 are appropriatelyselected, then the flexure 160 may be displaced or cupped away from thepumping chamber 140's bottom 150 during part of each pumping cycle, andmay be displaced or cupped towards the pumping chamber 140's bottom 150during the rest of each pumping cycle. As a result of such bipolaroperation of the pump 130, the displacement of the pumping flexure 160may be effectively doubled during each of the pump 130's pumping cycles(as compared to if the polarity of the input voltage was notperiodically reversed), thereby doubling the pump 130's output ofmedication 12. The output pressure of the medication 12 from the pump130 may also be increased by using bipolar operation of the pump 130.

If the pump 130 is operated so that the pumping flexure 160 is displaceddownwardly towards the pumping chamber 140's bottom 150, the diameter ofthe motor 138 may be selected to be less than the diameter of thepumping chamber 140, to better enable such downward displacement tooccur.

Generally, the above described bipolar operation of the pump 130 may belimited by depolarization of the piezoelectric disk 162 when it isreverse biased. Many ceramic materials substantially degrade inperformance if operated for short periods of time at reversed polarityelectric fields in excess of about 50 KV/cm. Hence, the above-describeddoubling effect of bipolar operation of the pump 130 may besubstantially compromised by this limitation. Mono-polar operation ofthe pump 130 at high voltages and electric fields may be capable ofachieving flows and pressure outputs which are comparable to those ofsuch bipolar operation at lower voltages and electric fields.

The pump 130 may be driven by any suitable electrical driving meanswhich may be attached to the motor 138's wires 170, 172. Such anelectrical driving means may include a means for controlling thedisplacement of the pumping flexure 160 during each pumping cycle of thepump 130, (such as by suitably varying the polarity and/or the amount ofthe voltage applied to the motor 138's wires 170, 172); and/or mayinclude means for varying the frequency of the pumping cycles of thepump 130, (such as by suitably varying the frequency of the voltageapplied to the motor 138's wires 170, 172). Such electrical drivingmeans may also include a suitably programmed microprocessor for helpingthe electrical driving means to perform its above functions.

It has been discovered that another important feature of the pump 130 isthat the pump 130 may be made so that its piezoelectric motor 138 andits pumping flexure 160 may minimize, or even eliminate, undesirableforward flow of the medication 12 into the pumping cavity 140 throughthe inlet valve 134, in the event the medication 12 at the inlet port142 is overpressurized beyond the nominal designed input pressure. Suchforward flow of the medication 12 is undesirable since in manyapplications for the pump 130 there may be adverse consequences if thathappens. For example, if the pump 130 were used in a medical device fordelivering the medication 12 to a patient, such undesirable forward flowof the medication 12 might result in the possibility of injury or deathto the patient due to an overdose of the medication 12.

There are several ways in which the pump 130 may be made so that itspiezoelectric motor 138 and its pumping flexure 160 may minimize, oreven eliminate, such undesirable forward flow of the medication 12 inthe event of such overpressurization. For example, the various parts ofthe pump 130 may be sized so that, when there is no voltage applied tothe pump 130's wires 170, 172, the bottom surface of the pumping flexure160 will be in physical contact with the top surface of the inlet valve134's flexure 154. Alternatively, the pumping flexure 160's bottomsurface may be provided with a raised boss (not illustrated) which willbe in contact with the top surface of the inlet valve 134's flexure 154when there is no voltage applied to the pump 130. Thus, either thepumping flexure 160's bottom surface, or its raised boss, will rest on,and provide an interference fit with, the inlet valve flexure 154 whenthere is no voltage applied to the pump 130. (Such an interference fitmay also assist in holding the inlet valve flexure 154 closed, to helpprevent back flow of the medication 12 through the pump 130, in theevent the pump 130 is subjected to a reverse pressure.)

Accordingly, before there is any undesired forward flow of themedication 12 into the pumping cavity 140 caused by suchoverpressurization of the medication 12, the force generated by thatoverpressurization on the bottom surface of the flexure 154 would haveto overcome at least three things. First, it may have to lift the weightof the pumping flexure 160 and the motor 138. Second, it would have toovercome the stiffness of both the pumping flexure 160 and the motor138, which may be much stiffer than the inlet valve flexure 154. Third,it would have to overcome the effect of any pre-load of the pumpingflexure 160's bottom surface, or its raised boss (if any), on the inletvalve flexure 154. Accordingly, these three factors may result in thepump 130 having a significantly lower forward bleed rate of themedication 12 into the pumping cavity 140 in the event of suchoverpressurization, than would be the case if the pumping flexure 160(or its raised boss) was not resting on the top surface of the inletvalve 134's flexure 154 when there is no voltage applied to the pump130.

In addition, it has also been discovered that the undesired forwardbleeding of the medication 12 into the pumping cavity 140 in the eventof such overpressurization of the medication 12 (and the undesired backflow of the medication 12 into the pumping cavity 140, in the event thepump 130 is subjected to a reverse pressure), may also be reduced, oreven eliminated, by reversing the polarity of the voltage which isapplied to the motor 138's wires 170, 172. Such reversed polarity wouldcause the motor 138, and the pumping flexure 160, to assume a cuppedshape, with the center of the pumping flexure 160 (or its raised boss),being pushed down against the inlet valve 134's flexure 154; therebytending to hold the flexure 154 (or its raised boss) seated tightlyagainst the inlet valve 134's valve seat 152, despite any suchoverpressurization of the medication 12, and despite any such reversepressure of the medication 12.

It has also been discovered that, since the motor 138 acts as acapacitor with very low leakage, and can maintain a cupped shape undersuch reversed polarity with little additional electrical power input,the pump 130 is very efficient compared to a pump which utilizedelectromagnetic or thermal effects, where substantial electrical powerwould have to be input at all times in order to maintain such a cuppedshape. In addition, the charge on the capacitor (the motor 138), may inpart be recovered when the capacitor is discharged (when the inputvoltage is reduced or interrupted), to produce an output stroke, therebyfurther increasing the electrical energy efficiency of the pump 130.

Such electrical energy efficiency may be extremely important, such as ifthe pump 130 is used in a battery powered, implanted medical device.This is because any given battery will need to be recharged or replaced(which might require surgery), much less frequently, as compared to apump 130 which was not so electrical energy efficient.

An important consideration in the design of the pump 130 may be theselection of the particular bonding material 168 which is used to bondthe motor 138 to the pumping flexure 160. It has been discovered thatthis may be important for at least two reasons.

First, it has been discovered that if a hard bonding material 168, suchas an epoxy, is used, and if the pump 130 is exposed to a wide operatingtemperature range (such as from about -40° C. to about 80° C.), then thepump 130 may experience operating difficulties. Such operatingdifficulties may include changes in the fit-up between the motor 138'spiezoelectric disk 162 and the pumping flexure 160; closure problemswith the inlet valve 134, due to static deflection of the pumpingflexure 160; and changes in the volume of the medication 12 which isdelivered by the pump 130 during each of its pumping cycles. This may bebecause the thermal expansion characteristics of the materials fromwhich the piezoelectric disk 162 and the pumping flexure 160 are madegenerally differ significantly from each other, giving rise tointerfacial shear between the disk 162 and the pumping flexure 160.

In addition, it has also been discovered that if the bonding material168 is selected to be a hard bonding material 168 (such as an epoxy),then the motor 138's center will only deflect about 15% of thedeflection the motor 138's center would experience if the motor 138 werefree-standing by itself. This may be because a hard bonding material 168may not be able to provide a low-shear joint between the piezoelectricdisk 162 and the pumping flexure 160. Thus, most of the electricalenergy which is delivered to such a hard-bonded piezoelectric disk 162may be wasted in a futile attempt by the piezoelectric disk 162 toradially compress the relatively stiff pumping flexure 160.

On the other hand, it has been further discovered that if the bondingmaterial 168, which is used to bond the motor 138 to the pumping flexure160, is selected to be a soft, gel-like polymer, such as siliconerubber, then all of the above operating difficulties may be reduced, oreven eliminated.

In addition, it has also been discovered that if a soft bonding material168 is used, then the deflection of the motor 138's center will beincreased up to about 85% of the deflection the motor 138's center wouldexperience if the motor were free-standing by itself. That results in aremarkable gain of up to about 5 times in the length of the motor 138'suseful pump stroke (as compared to when a hard bonding material 168 isused), with a corresponding remarkable reduction in the amount ofelectrical energy which is wasted by the pump 130. Thus, if a softbonding material 168 is used, the pump 130's motor 138 utilizes itsinput energy unusually efficiently to cause maximum deflection of thepumping flexure 160. This, is turn, causes the pump 130 to deliver themaximum amount of medication 12 to its outlet port 146 for any givenamount of input electrical energy. As has been mentioned, this energyefficiency may be extremely important, such as if the pump 130 is usedin a battery powered, implanted medical device. This is because anygiven battery will need to be recharged or replaced (which might requiresurgery), much less frequently, as compared to a pump 130 which was notso energy efficient.

It is theorized that a soft, gel-like bonding material 168 may work sowell because although it may have the ability to transmit verticalmotion between the piezoelectric disk 162 and the pumping flexure 160,it may have very little ability to transmit shear forces between thosetwo elements of the pump 130. Thus, the use of a soft, gel-like polymeras the bonding material 168 may relieve the stresses in the interfacebetween the motor 138's piezoelectric disk 162 and the pumping flexure160. This may reduce the shear loads between the disk 162 and pumpingflexure 160, thereby permitting better coupling therebetween. Reducingsuch shear loads and increasing such coupling may be desirable becauseit may enable the pump 130 to operate at unusually low driving voltages(as low as about 50.0 volts; because it may reduce the energyconsumption of the pump 130; and because it may enable the pump 130 tobe made extremely small.

In addition, it has been discovered that the pump 130 is very efficientwhen operated at comparatively low average flow rates, such as about 1.0microliters/second, and when the pump 130 is operated at comparativelylow average operating pressures, such as about 1.0 to about 200 mm Hg.This is because at such low flow rates and operating pressures the flowof the medication 12 through the pump 130 tends to be laminar; meaningthat less energy is lost due to friction, turbulence, and geometricshape changes of the medication 12.

For example, the example pump 130, whose physical parameters were setforth above, uses about 1/100th of the energy, and occupies about 1/50thof the space as compared to a peristaltic pump of equal capacity whichis now used in an existing drug delivery device.

It has also been discovered that another important consideration in thedesign of the pump 130 may be to maintain a pre-determined residualamount of medication 12 in the pumping cavity 140 at all times duringthe pump 130's pumping cycle. For example, for a pump 130 having a veryshallow pumping cavity 140 and a very small deflection or cupping of themotor 138 and the pumping flexure 160 (such as the example pump 130whose physical parameters were set forth above), the pump 130 may bedesigned so that from about 10% to about 75% of the volume of themedication 12 in the pumping cavity 140, and preferably about 50% of thevolume of the medication 12 in the pumping cavity 140, is left in thepumping cavity 140 during each pumping cycle.

It has been discovered that maintenance of such a residual amount of themedication 12 in the pumping cavity 140 at all times during the pump130's pumping cycle may be important for at least two reasons. First,the pump 130 may be operated at a higher pumping cycle rate (frequency),than would otherwise be the case. This is because it can be shown thatthe time it would take for the pumping flexure 160 to completely pumpall of the medication 12 out of the pumping cavity 140 (assuming therewere no flexure supports 148 and inlet valve 134), becomes infinite asthe pumping flexure 160 approaches the bottom of the pumping cavity 140.In such a case, the pumping flexure 160 would be attempting to removethe residual medication 12 in the pumping cavity 140 in the presence ofa high-shear condition created by the extreme proximity of the pumpingflexure 160 to the pumping cavity 140's bottom 150. This would result inan increased viscous drag which, in turn, would create a decreasedefficiency and a need to operate the pump 130 at a lower pumping cyclerate, thereby undesirably limiting the dynamic range of the pump 130.

The second reason that it may be important to maintain a residual amountof the medication 12 in the pumping cavity 140 at all times is that theresidual medication 12 in the pumping cavity 140 may provide a lowresistance path for the medication 12 as it enters or leaves the pumpingcavity 140. This is because of the fluid viscosity of the medication 12;because of the extremely small dimensions of the pumping cavity 140; andbecause of the extremely small dimensions of the components housedwithin the pumping cavity 140.

Maintenance of the desired residual amount of the medication 12 in thepumping cavity 140 at all times during the pump 130's pumping cycle maybe achieved in any suitable way, such as by suitably selecting the depthof the pumping cavity 140; and by suitably controlling the depth towhich the pumping flexure 160 may enter the pumping cavity 140, such asby suitably selecting the height and/or location of the flexure supports148 and the inlet valve 134.

From the disclosures herein, it is seen that it is possible toselectively design a pump 130 having any particular desired medication12 flow rate and output pressure. This may be done by selectivelyadjusting one or more of the pertinent parameters, such as: (a) thefrequency of the input voltage (i.e., the pumping cycle rate of the pump130); (b) the polarity and amount of the input voltage (i.e., the amountof medication 12 delivered by the pump 138 during each of its pumpingcycles); (c) the power of the motor 138, and the number, size and shapeof its piezoelectric and cover disks 162, 164; (d) the properties, size,shape and thickness of the bonding material 168; (e) the number, size,shape, and location of the inlet and outlet ports 142, 146, the inletand outlet cavities 153, 159, the inlet and outlet valve seats 152, 155,the pumping flexure supports 148, the pumping cavity 140, the channel147, and the outlet valve cavity 144; and the size, shape, location,thickness, resiliency, elasticity, and stiffness of the inlet valveflexure 154, the pumping flexure 160, and the outlet valve flexure 157.

MICROMACHINED DIAPHRAGM PUMP 130 HAVING INTEGRAL VALVING AND A CENTRALLYLOCATED INLET PORT (FIGS. 16-17): MANUFACTURE

The pump 130's substrate 132 may be made from any suitable strong,durable material, which is compatible with the medication 12, and inwhich the inlet port, the inlet cavity 153, the inlet valve seat 154,the pumping cavity 140, the flexure supports 148, the flexure supportbosses 156, the channel 147, the outlet valve cavity 144, the outletvalve seat 155, and the outlet cavity 159 may be manufactured in anysuitable way, such as by using any suitable etching, molding, stampingand machining process. Such a machining process may include the use ofphysical tools, such as a drill; the use of electromagnetic energy, suchas a laser; and the use of a water jet.

The membrane 136 may be made from any suitable strong, durable,flexible, material which is compatible with the medication 12. Themembrane 136 may also be elastic.

If the pump 130 is intended to pump a medication 12 which is to besupplied to a human or an animal, then any part of the pump 130 which isexposed to the medication 12 should be made from, and assembled orbonded with, non-toxic materials. Alternatively, any toxic materialwhich is used to manufacture the pump 130, and which is exposed to themedication 12 during use of the pump 130, may be provided with anysuitable non-toxic coating which is compatible with the medication 12.

Suitable materials for the substrate 132 and the membrane 134 may bemetals (such as titanium), glasses, ceramics, plastics, polymers (suchas polyimides), elements (such as silicon), various chemical compounds(such as sapphire, and mica), and various composite materials. Ingeneral, because the dimensions of the pump 130's various components maynot be as critical as the dimensions of the various components of theregulator 32 of FIGS. 1-2, there may be more options regarding thematerials from which the pump 130's substrate 132 and membrane 136 maybe made.

The substrate 132 and the membrane 136 may be assembled or bondedtogether in any suitable leak-proof way, such as those described abovefor assembling or bonding together the regulator 32's substrate 34 andmembrane 36 of FIGS. 1-2, except for those differences, if any, whichwill be made apparent by an examination of all of the Figures anddisclosures in this document.

The manufacture of the pump 130's inlet port 142, inlet cavity 153,inlet valve seat 154, pumping cavity 140, pumping flexure supports 148,input valve flexure support bosses 156, channel 147, outlet valve cavity144, outlet valve seat 155, outlet cavity 159 and outlet port 146 may bedone in any suitable way, such as by using processes which are the sameas, or similar to, those used for manufacturing the radial flowregulator 32's inlet channels 38, inlet cavity 40, regulator seat 42,outlet cavity 52 and outlet port 54, except for those differences, ifany, which will be made apparent by an examination of all of the Figuresand disclosures in this document.

One example of how the example pump 130, having the physical parameterswhich were set forth above, may be manufactured will now be given. Thestarting point may be a 76.2 mm diameter wafer of Corning 7740 Pyrexglass, which will form the pump 130's substrate 132.

The inlet cavity 153, the inlet valve seat 152, the inlet valve flexuresupport bosses 156, the pumping cavity 140, the pumping flexure supports148, the channel 147, the outlet valve cavity 144, the outlet valve seat155, and the outlet cavity 159 may be formed in the substrate 132 in anysuitable way. One suitable way may be to first etch into the substrate,to a depth of about 16 microns, what will be the inlet cavity 153, theinlet valve seat 152, the pumping cavity 140, the inlet valve flexuresupport bosses 156, the channel 147, the outlet valve cavity 144, andthe outlet cavity 159. Then, what will be the inlet cavity 152, thepumping cavity 140, the channel 147, the outlet valve cavity 144, andthe outlet cavity 159 may be etched into the substrate about anadditional 9 microns. What will be the pumping flexure supports 148 andthe outlet valve seat 155 may not be etched at all.

The inlet and outlet ports 142, 146 may then be formed in the substrate132 in any suitable way. The structure, operation, theory andmanufacture of the pump 130's inlet and outlet ports 142, 146 may be thesame as, or at least similar to, those of the radial flow regulator 32'soutlet port 54 of FIGS. 1-2, except for those differences, if any, whichwill be made apparent by an examination of all of the Figures anddisclosures in this document.

Next, a nominal layer of one or more corrosion-resistant materialsubstances may then be deposited onto all of the surfaces of the inletport 142, the inlet cavity 153, the inlet valve seat 154, the inletvalve flexure support bosses 156 (except for the top surfaces of theflexure support bosses 156), the pumping cavity 140, the pumping flexuresupports 148, the channel 147, the outlet valve cavity 144, the outletvalve seat 155, the outlet cavity 159, and the outlet port 146. Thestructure, operation, theory and manufacture of such a layer of one ormore corrosion-resistant substances for the pump 130 may be the same as,or at least similar to, those of the layer of one or morecorrosion-resistant substances for the radial flow regulator 32 of FIGS.1-2, except for those differences, if any, which will be made apparentby an examination of all of the Figures and disclosures in thisdocument.

It has been discovered that such a layer of corrosion-resistantsubstance(s) may serve at least two important functions, in addition toits corrosion-resistant function, if the membrane 136 is anodicallybonded to the substrate 132. First, the layer of corrosion-resistantsubstance(s) may prevent the pumping flexure 160 from sticking to thepumping flexure supports 148 during the anodic bonding process. Second,it may also prevent the outlet valve flexure 157 from sticking to theoutlet valve seat 155 during the anodic bonding process.

Manufacturing the inlet valve flexure 154 and mounting it to the tops ofthe inlet valve flexure support bosses 156 may be done in any suitableway. The structure, operation, theory and manufacture of the pump 130'sinlet valve flexure 154 and the bonding of the inlet valve flexure 154to its substrate 132 is the same as, or at least similar to, that of theradial flow regulator 32's membrane 36, and the bonding of the membrane36 to its substrate 34, except for those differences, if any, which willbe made apparent by an examination of all of the Figures and disclosuresin this document.

For example, the inlet valve flexure 154 may be manufactured from aprime silicon wafer having a boron-doped epitaxial silicon layer whichhas been deposited onto its top surface. Since the boron doped epitaxialsilicon layer will ultimately form the pump 130's inlet valve flexure154, the layer's thickness will depend on the desired thickness of theinlet valve flexure 154. The boron-doped epitaxial silicon layer, andthus the inlet valve flexure 154 may be about 9 microns thick, forexample. The boron doping may be in excess of 3×10¹⁹ atoms of boron percubic centimeter, which conveys a dramatic etch-resistance to theepitaxial silicon layer in silicon etchants based on ethylene diamine.

First, the boron-doped silicon wafer may be cleaned; a thin chromemetallization layer may be applied on top of the wafer's boron-doped topsurface; and a thin layer of any suitable photoresist may then beapplied on the top of the chrome layer, and then dried. An image of theoutline of the inlet valve flexure 154 may then be exposed onto thephotoresist, and then developed; after which the boron-doped siliconwafer may be cleaned and dried.

As a result of the forgoing procedure, the chrome layer will now bear animage, unprotected by the photoresist, of the outline of the inlet valveflexure 154. The unprotected portion of the chrome layer may then beetched away; resulting in an image of the outline of the inlet valveflexure 154 having been formed on the silicon wafer's boron-doped topsurface. The image of the outline of the inlet valve flexure 154 maythen be etched into silicon wafer's boron-doped top surface, in anysuitable way, such as by using an aggressive, isotropic etchant, to adepth which is deeper than the thickness of the silicon wafer'sboron-doped top surface. Then the photoresist and chrome layers may beremoved by any suitable means; and the boron-doped silicon wafer may becleaned and dried.

The non-doped surface of the boron-doped silicon wafer may then beetched away in any suitable way, such as by the use of an ethylenediamine etchant; thereby leaving the desired inlet valve flexure 154free standing. The free standing inlet valve flexure 154 may then bealigned with, and bonded to its bosses 156 in any suitable way, such asin a way which is the same as, or at least similar to, that used to bondthe radial flow regulator 32's membrane 36 to its substrate 34, exceptfor those differences, if any, which will be made apparent by anexamination of all of the Figures and disclosures in this document. Onesuitable way may be to use anodic bonding. During the bonding process,the inlet valve flexure 154 may be held in place on its bosses 156 inany suitable way, such as by using small pins, or by using electrostaticforces.

Manufacturing the membrane 136 and bonding it to the glass wafer (whichis the substrate 132) may be done in any suitable way. The structure,operation, theory and manufacture of the pump 130's membrane 136 and thebonding of the membrane 136 to its substrate 132 to form a silicon/glasssandwich is the same as, or at least similar to, the manufacturing ofthe radial flow regulator 32's membrane 36, and the bonding of themembrane 36 to its substrate 34 to form a silicon/glass sandwich, exceptfor those differences, if any, which will be made apparent by anexamination of all of the Figures and disclosures in this document.

The piezoelectric motor 138 may be manufactured by forming thepiezoelectric and cover disks 162, 164 in any suitable way, such as byusing any suitable etching, molding, stamping, and machining process.The disks 162, 164 may be of comparable thickness, and may be firmlybonded to each other in any suitable way, such as by using a silverepoxy bonding material.

The piezoelectric disk 162 may be manufactured from any suitablepiezoelectric material, such as a piezoelectric ceramic material calledPZT5H, which is made by Vernitron Corp., located in Bedford, Ohio.Preferably, the top and bottom surfaces of the piezoelectric disk 162may be provided with a thin conductive coating of any suitable metal,such as nickel, to make it more convenient to electrically excite thepiezoelectric disk 162. The cover disk 164 may be manufactured from anysuitable electrically conductive, relatively stiff, resilient material.A metal, such as stainless steel, may be suitable.

The wire 170 may be electrically connected to the motor 138's cover disk164 in any suitable way, such as by using a bead 174 of electricallyconductive epoxy material. The wire 172 may be electrically connected tothe bottom of the piezoelectric disk 162 in any suitable way, such as byusing gold wire bonding, as practiced in the semiconductor industry. Thewire 172 may have a diameter selected to be equal to the desiredthickness of the layer of bonding material 168, thereby defining thedesired spacing between the piezoelectric disk 162 and the flexure 160.

The motor 138's piezoelectric disk 162 may be bonded to the pumpingflexure 160's top surface in any suitable way, such as by using a layerof bonding material 168. The bonding material may be a hard bondingmaterial (such as an epoxy); but preferably, it may be a soft, gel-likepolymer, such as silicone rubber. For example, a suitable soft, gel-likepolymer may be Sylgard 527 brand silicone rubber, made by the DowCorning Company, located in Midland, Mich.

The manufacture of only one pump 130 was described above. However, itwill be appreciated that on any pair of glass and silicon wafers thesubstrates 132 and membranes 136 for numerous pumps 130 could bemanufactured simultaneously in a manner similar to that described above.If such is the case, an array of substrates 132 may be simultaneouslyetched in the glass wafer. Then an array of inlet valve flexures 154 maybe manufactured, aligned, and bonded to their respective bosses 156;after which the silicon and glass wafers for the substrates 132 andmembranes 136 may be aligned and bonded together. Then, all of themembranes 136 may be formed simultaneously by grinding and etching thesilicon wafer for the membranes 136 to its desired final thickness.Next, a piezoelectric motor 138 for each pump 130 may be manufacturedand bonded, along with its wires 170, 172, to its respective pump 130.The silicon/glass substrate 132/membrane 136 sandwich may then bedivided by any suitable means (such as dicing) into individual chips,each chip bearing at least one pump 130.

One of the advantages of using the etching and anodic bonding processeswhich were described in detail above is that such processes enable highquality, very reliable pumps 130 to be mass produced in great numbers ata cost so low that the pump 130 may be considered to be disposable. Inaddition, it should also be noted that the pump 130 is stunning in itssimplicity since its membrane 136 serves as both the pumping flexure 160and the outlet valve flexure 157; and since the parts which move (i.e.,the inlet valve flexure 154, the pumping flexure 160, the motor 138 andthe outlet valve flexure 157) merely bow during operation. Further,because the raw materials from which the pump 130 may be made may bevery inexpensive, such as glass and silicon, the cost of the pump 130may held to a very low level.

MICROMACHINED DIAPHRAGM PUMP 180 HAVING INTEGRAL VALVING AND AN EDGELOCATED INLET PORT (FIGS. 18-19): STRUCTURE, OPERATION, THEORY ANDMANUFACTURE

The micromachined diaphragm pump 180 which is illustrated in FIGS. 18-19is the same as, or at least similar to, the pump 130 of FIGS. 16-17 inits structure, operation, theory and manufacture, except for thosedifferences which will be made apparent by an examination of all of theFigures and all of the disclosures in this document. Accordingly, therespective parts of the pump 180 of FIGS. 18-19 have been given the samereference numerals as the corresponding parts of pump 130 of FIGS.16-17, for clarity and simplicity.

Turning again to FIGS. 18-19, the pump 180's inlet valve 134 maycomprise a one-way flapper valve having a cantilevered flexure 154 oneend of the flexure 154 may be mounted to its support boss 156, while theflexure 154's free end may lay over the inlet valve seat 152 when novoltage is applied to the motor 138's wires 170, 172. Although oneparticular form of one-way inlet valve 134 is illustrated in FIGS.17-18, the pump 180's one-way inlet valve 134 may be any other suitableone-way valve, such as the one-way valves which are disclosed in thisdocument.

As seen, the pump 180's inlet valve 134 may be located near an edge ofthe pumping cavity 140. It has been discovered that locating the inletvalve 134 near an edge of the pumping cavity 140 may have at least twoadvantages. First, it may enable the priming of the pumping cavity 140to occur in a very automatic, reproducible way when the pump 180 isturned on. Such priming may occur because the surface tension of themedication 12 may initially draw the medication 12 in around theperimeter of the pumping cavity 140, where the surface tension curvatureforces are the strongest. Such priming by surface tension is given bythe following equation:

    ΔP=γ(1/r.sub.C1 +1/r.sub.C2)

where ΔP is pressure, where γ is the surface tension, and r_(C1) andr_(C2) are the two orthogonal radii of curvature describing a point onthe fluid's surface. Near the periphery of the pumping cavity 140, oneradius will be equal to approximately the pumping cavity 140's radius,while the other radius will be equal to one-half of the pumping cavity140's depth. Since the flexure 160's center may be bowed away from thepumping cavity 140's bottom, resulting in lower surface tension primingpressures there, the initiation of priming around the pumping cavity140's periphery will generally result in a more natural and reproducibletotal priming.

Such priming of the pumping cavity 140 may be advantageous because ithas been discovered that it may help to eliminate any "dead spots" orbubbles inside of the pump 180. Not having any such "dead spots" orbubbles in the pump 180 is desirable because such bubbles may get caughtin the inlet and outlet valves 134, 137 and cause high surface tensionΔP's because of the small dimensions of the inlet and outlet valves 134,137; and thus may adversely affect the operation of the inlet and outletvalves 134, 137. In addition, if the pump 180 is used in a medicaldevice, such bubbles may result in dangerous, or even fatal, embolismsin the patient.

The second advantage of locating the inlet valve 134 near an edge of thepumping cavity 140 is that it has been discovered that such a locationfor the inlet valve 134 may also enable the pump 180 to clean itself ofany bubbles which may have formed in its pumping cavity 140 for anyreason. This is because during operation of the pump 180 the flow of themedication 12 will be from the inlet port 142, across the pumping cavity140, through the channel 147, across outlet valve cavity 144, and out ofthe outlet port 146, thereby tending to sweep any such bubbles out ofthe pumping cavity 140, the channel 147, the outlet valve cavity 147,the outlet cavity 159, and the outlet port 146.

As seen in FIGS. 18 and 19, the eleven membrane supports 148 maycomprise cylindrical pins having any suitable diameter, such as about0.5 mm. As was mentioned above, it has been discovered that usingrelatively small cylindrical pin shaped flexure supports 148 (FIGS.18-19), instead of relatively large radial spine type flexure supports148 (FIGS. 16-17), may be advantageous for at least four reasons. First,they may have less flow resistance to the medication 12 being pumped bythe pump 130. Second, they may have less adverse impact on the primingof the pumping cavity 140. Third, they may have less propensity toundesirably trap bubbles within the pumping cavity 140. Fourth, they mayhave less of an adverse impact on the ability of the medication 12 tosweep any bubbles out of the pumping cavity 140 during operation of thepump 130.

Although eleven, cylindrical flexure supports 148 are illustrated inFIGS. 17-18, there may be fewer or more flexure supports 148, and eachflexure support 148 may have any other suitable size and shape.

By way of example, the diaphragm pump 180 may weigh about 0.6 grams; andmay have the following physical parameters. The substrate 132 may be asquare having sides about 1.30 cm long, and may have a thickness ofabout 0.5 mm. The membrane 136 may have a thickness of about 25 microns.The inlet valve flexure 154 may have a thickness of about 9.0 microns, awidth of about 1600 microns, and a length of about 2000 microns. Thepumping cavity 140 may have a diameter of about 1.07 cm, and the outletvalve cavity 144 may have a diameter of about 3.4 mm. The cavities 140,144 may each have a depth of about 25.0 microns. The channel 147 mayhave a width of about 0.5 mm, a length of about 1.0 mm, and a depth ofabout 25 microns. The inlet and outlet ports may have a minimum diameterof about 100 microns. The flexure supports 148 and the outlet valve seat154 may each have a height of about 25 microns. The inlet valve seat 152and the inlet valve flexure bosses 156 may each have a height of about9.0 microns. The piezoelectric motor 138 may act as about a 0.02 μFcapacitor; and its disks 162, 164 may each have a thickness of about0.15 mm and a diameter of about 1.1 cm. The bonding material 168, whichbonds the disk 162 to the pumping flexure 160's top surface may have athickness of about 50.0 microns thick; and the wires 170, 172 may have adiameter of about 50.0 microns. This example pump 180 may deliver about0.1-1.0 microliters of the medication 12 per pumping cycle; and operateat a frequency of from about 0.0 to about 25.0 pumping cycles persecond.

During operation of the pump 180, when any suitable source of electricalpower is applied to its motor 138's wires 170, 172, or when the voltageof that source of electrical power is increased, the centers of themotor 138 and the pumping flexure 160 tend to bow away from the pumpingcavity 140's bottom 150 to form a cupped shape. As this happens, theoutlet valve 137 closes; the inlet valve 134 opens; and the medication12 is drawn into the pumping cavity 140 through the inlet port 142 andthe inlet valve 134.

On the other hand, when the source of electrical power to the motor138's wires 170, 172 is reduced, is interrupted, or has its polarityreversed, the centers of the motor 138 and the pumping flexure 160 tendto automatically return to their original flat configurations (if thepower is reduced or interrupted), or tend to be displaced towards thepumping cavity 140's bottom 150 (if its polarity is reversed). As thishappens, the inlet valve 134 is closed; the outlet valve 137 is opened;and the medication is pumped from the pumping cavity 140 into thechannel 147, into the outlet valve cavity 144, and out through theoutlet valve 137 and the outlet port 146.

MICROMACHINED DIAPHRAGM PUMP 190 HAVING MODULAR VALVING AND AN EDGELOCATED INLET PORT (FIGS. 20-22): STRUCTURE

The micromachined diaphragm pump 190 which is illustrated in FIGS. 20-22is the same as, or at least similar to, the pumps 130, 180 of FIGS.16-19 in its structure, except for those differences which will be madeapparent by an examination of all of the Figures and all of thedisclosures in this document. Accordingly, the respective parts of thepump 190 of FIGS. 20-22 have been given the same reference numerals asthe corresponding parts of the pumps 130, 180 of FIGS. 16-19, forclarity and simplicity.

Although, as best seen in FIGS. 20-21, the pump 190's four pumpingflexure supports 148 are arcuate in shape, and surround the outlet port146, there may be fewer or more of the pump 190's pumping flexuresupports 148, and each such pumping flexure support 148 may have anyother suitable size, shape and location. Preferably, spaces 206 may beprovided between the pumping flexure supports 148, in order to helpprovide fluid paths for the medication 12 as it travels from the inletport 142 to the outlet port 144. Alternatively, the spaces 206 may beeliminated, and the four arcuate pumping flexure supports 148 may bemerged into an outlet valve seat 155 having any suitable size and shape.

While the pumps 130, 180 may have their inlet valves 134 located insideof their pumping cavities 140, the pump 190's inlet valve 134 may besecured to the exterior of its substrate 132 over its inlet port 142, asseen in FIG. 20.

Similarly, while the pumps 130, 180 may have their outlet valves 137 andtheir outlet ports 146 located on the inside of their outlet valvecavities 144, (with a channel 147 being provided between their pumpingcavities 140 and their outlet valve cavities 144); the pump 190 may havemay have no channel 147, may have no outlet valve cavity 144, may haveits outlet port 146 located in the center of its pumping cavity 140, andmay have its outlet valve 137 secured to the exterior of its substrate132 over its outlet port 146, as seen in FIG. 20.

The pump 190's one-way inlet and outlet valves 134, 137 may be anysuitable one-way valve, such as the one-way valves which are disclosedin this document. For example, the one-way valve 300 of FIGS. 30-31 maybe suitable. The structure, operation, theory and manufacture of theone-way valve 300 illustrated in FIGS. 30-31 will be discussed in detailbelow.

The medication 12 may be conveyed to the inlet valve 134 and conveyedfrom the outlet valve 137 in any suitable way, such as by using inletand outlet tubes 192, 194, respectively, which are secured to thesubstrate 132.

As seen in FIG. 20, the substrate 132 may be provided with an inletvalve recess 198, in order to provide an inlet valve gap 200 between thepump 190's substrate 132 and the inlet valve 134. The inlet valve gap200 may serve to permit the inlet valve 134's flexure 314 to deflecttowards the substrate 132 during flow of the medication 12 into thepumping cavity 140 while the pump 190 is operating. However, the inletvalve recess 198 may be eliminated, and the inlet valve gap 200 may beformed in any other suitable way, such as by providing a spacer betweenthe substrate 132 and the inlet valve 134, or by forming a raisedseparator on the substrate 132 and/or on the inlet valve 134.

Similarly, as also seen in FIG. 20, the substrate 132 may be providedwith an outlet valve recess 202, in order to provide an outlet valve gap204 between the substrate 132 and the outlet valve 137. The outlet valvegap 204 may serve to provide a circumferentially more uniform flow ofthe medication 12 from the pump 190's outlet port 146 to the outletvalve 137's inlet ports 306 during operation of the pump 190. However,the outlet valve recess 202 may be eliminated, and the outlet valve gap204 may be formed in any other suitable way, such as by providing aspacer between the substrate 132 and the outlet valve 137, or by forminga raised separator on the substrate 132 and/or on the outlet valve 137.

By way of example, the diaphragm pump 190 may weigh about 1.0 gram; andmay have the following physical parameters. The substrate 132 may be asquare having sides about 1.30 cm long; and a thickness of about 0.5 mm.The membrane 136 may have a thickness of about 25 microns. The pumpingcavity 140 may have a diameter of about 1.07 cm, and a depth of about 25microns. The inlet and outlet ports 142, 146 may have a minimum diameterof about 100 microns. The flexure supports 148 may have a height ofabout 25 microns. The piezoelectric motor 138 may act as about a 0.02 μFcapacitor; and its disks 162, 164 may have a thickness of about 0.15 mm,and a diameter of about 1.1 cm. The bonding material 168, which bondsthe disk 162 to the pumping flexure 160's top surface may be about 50.0microns thick; and the wires 170, 172 may have a diameter of about 50.0microns. This example pump 180 may deliver about 0.1-1.0 microliters ofthe medication 12 per pumping cycle; and operate at a frequency of fromabout 0.0 to about 25.0 pumping cycles per second.

MICROMACHINED DIAPHRAGM PUMP 190 HAVING MODULAR VALVING AND AN EDGELOCATED INLET PORT (FIGS. 20-22): OPERATION AND THEORY

The micromachined diaphragm pump 190 which is illustrated in FIGS. 20-22is the same as, or at least similar to, the pumps 130, 180 of FIGS.16-19 in its operation and theory, except for those differences, if any,which will be made apparent by an examination of all of the Figures andall of the disclosures in this document.

One of the significant features of the pump 190 is the simplicity of itssubstrate 132. That is, its substrate 132 has etched into it only thepumping cavity 140, the inlet and outlet ports 142, 146, and the pumpingflexure supports 148. Its substrate 132 does not have, or need, inlet oroutlet cavities 153, 159; inlet or outlet valve seats 152, 155; inletvalve flexure support bosses 156; a channel 147; or an outlet valvecavity 144. Such simplicity of the pump 190's substrate 132 inherentlymakes it easier and quicker to manufacture, with fewer steps, and at alower cost; as compared to the substrates 132 of the pumps 130, 180.

Another significant feature of the pump 190 is that its inlet and outletvalves 134, 137 may be modular in nature; making the pump 190 both easyand inexpensive to assemble. In addition, since the inlet and outletvalve 134, 137 may be modular in nature, they need not be necessarilysecured directly to the substrate 132. Instead, either or both of theinlet and outlet valves 134,137 may be located away from the substrate132, such as in the inlet and outlet tubes 192, 194, respectively.

During operation of the pump 190, when any suitable source of electricalpower is applied to the motor 138's wires 170, 172, or when the voltageof that source of electrical power is increased, the centers of themotor 138 and the pumping flexure 160 tend to bow away from the pumpingcavity 140's bottom 150, to form a cupped shape. As this happens, theoutlet valve 137 closes; the inlet valve 134 opens; and the medication12 is drawn into the pumping cavity 140 from the inlet tube 192 throughthe inlet valve 134 and the inlet port 142.

On the other hand, when the source of electrical power to the motor138's wires 170, 172 is reduced, is interrupted, or its polarity isreversed, the centers of the motor 138 and the pumping flexure 160 tendto automatically return to their original flat configurations (if thepower is reduced or interrupted), or tend to be displaced towards thepumping cavity 140's bottom 150 (if its polarity is reversed). As thishappens, the inlet valve 134 closes; the outlet valve 137 opens; and themedication 12 is pumped out of the pumping cavity 140 into the outlettube 194 through the outlet port 146 and the outlet valve 137.

Locating the inlet port 142 near an edge of the pumping cavity andlocating the outlet port 146 near the center of the pumping cavity mayhelp to prevent any bubbles from being trapped within the pumpingcavity. This is because the medication 12 will tend to sweep any suchbubbles out of the pumping cavity as it flows from the inlet port 142 tothe outlet port 146.

Undesired forward flow of the medication 12 through the pump 190 causedby overpressurization of the medication 12 in the inlet tube 192 may bereduced, or even eliminated, in at least three ways. First, it has beendiscovered that such undesired forward flow of the medication 12 duringoverpressurization may be reduced, or even eliminated, by changing thepumping flexure supports 148 into an outlet valve seat 155, in themanner described previously; and by sizing the pump 190 so that thebottom of the pumping flexure 160 rests on the top of the outlet valveseat 155 when no voltage is being applied to the pump 190's motor 138.

Thus, before there is any undesired forward flow of the medication 12into the pumping cavity 140 caused by such overpressurization of themedication 12, the force generated by that overpressurization on thebottom surface of the pumping flexure 160 would have to overcome atleast three things: First, it may have to lift the weight of the pumpingflexure 160 and the motor 138. Second, it would have to overcome thestiffness of both the pumping flexure 160 and the motor 138, which maybe much stiffer than the inlet valve flexure 314. Third, it would haveto overcome the effect of any pre-load of the pumping flexure 160'sbottom surface, or its raised boss (if any), on the outlet valve seat155. Accordingly, these three factors may result in the pump 130 havinga significantly lower forward bleed rate of the medication 12 into thepumping cavity 140 in the event of such overpressurization, than wouldbe the case if there were no outlet valve seat 155, or if the pumpingflexure 160 (or its raised boss) was not resting on the top surface ofthe outlet valve seat 155 when there is no voltage applied to the pump130.

Second, it has also been discovered that the undesired forward bleedingof the medication 12 through the pump 190 in the event of suchoverpressurization of the medication 12 may also be reduced, or eveneliminated, by reversing the polarity of the electric power which isapplied to the motor 138's wires 170, 172. This causes the motor 138,and the pumping flexure 160, to tend assume a cupped shape, with thecenter of the membrane 136's pumping portion 160 being pushed againstthe outlet valve seat 155 (assuming the pumping flexure supports 148were changed into an outlet valve seat 155, in the manner describepreviously); thereby preventing the medication 12 from exiting thepumping cavity 140 through the outlet port 154, despite suchoverpressurization of the medication 12.

Third, it has been discovered that the undesired forward bleeding of themedication 12 through the pump 190 in the event of suchoverpressurization of the medication 12 may also be reduced, or eveneliminated, by mounting the pump 190 so that the upper surface of themotor 138 is exposed to the medication 12 at the pressure of themedication 12 in the inlet 192. In such an event the pump 190 may act asa flow regular, similar to the flow regulator 32 of FIGS. 1-2. That is,the pump 190's outlet valve seat 155 (assuming the pumping flexuresupports 148 were changed into an outlet valve seat 155, in the mannerdescribe previously); and the corresponding portion of its pumpingflexure 160 may operate in a fashion similar to that previouslydescribed regarding the flow regulator 32's regulator seat 42 and itsflexure 28. That is, the pump 190's outlet valve seat 155 and thecorresponding portion of its pumping flexure 160 may regulate the flowrate (Q) of the medication 12 through the pump 190 within apre-determined range of the flow rate (Q) and the driving pressuredifference (P), and to completely shut off the flow rate (Q) of themedication 12 if the driving pressure difference (P) of the medication12 between the pump 190's inlet and outlet ports 142, 146 exceeds apre-determined value.

The maximum permissible flow rate (Q) of the medication 12 through thepump 190 may also be regulated in at least two additional ways. First,it may be regulated by adjusting the height of the inlet valve gap 200in any suitable way, such as by selecting the depth of the inlet valverecess 198 and by selecting the thickness of the inlet valve 134'sflexure 314. The height of the inlet valve gap 200 controls the flowrate (Q) because the flexure 314's maximum deflection during operationof the pump 190 is limited by the height of the inlet valve gap 200.That is, as the height of the inlet valve gap 200 is decreased, theflexure 314's maximum deflection is also decreased, thereby reducing themaximum flow rate (Q) of the medication 12 through the inlet valve 134for any given driving pressure difference (P) (and vice versa).

The second additional way that the maximum permissible flow rates (Q) ofthe medication 12 through the pump 190 may be regulated is bydischarging the medication 12 into the pumping cavity 140 through one ormore inlet ports 142a in the substrate 132 that are placed around theperimeter of the inlet valve flexure 304, rather than coaxial with theinlet valve 134, as shown in FIG. 20A. If that is done, theconfiguration of the inlet valve 134 may match that of the radial flowregulator 32 described above, and may regulate the flow rate (Q) of themedication 12 through the pump 190 within a pre-determined range of (Q)and driving pressure difference (P), and may completely shut off theflow rate (Q) of the medication 12 if the driving pressure difference(P) of the medication 12 at the inlet 192 exceeds a pre-determinedamount.

MICROMACHINED DIAPHRAGM PUMP 190 HAVING MODULAR VALVING AND AN EDGELOCATED INLET PORT (FIGS. 20-22): MANUFACTURE

The micromachined diaphragm pump 190 which is illustrated in FIGS. 20-22is the same as, or at least similar to, the pumps 130, 180 of FIGS.16-19 in its manufacture, except for those differences, if any, whichwill be made apparent by an examination of all of the Figures and all ofthe disclosures in this document.

The pump 190's inlet and outlet valve recesses 198, 202 may bemanufactured in any suitable way, such as by using an etching processsimilar to that used to manufacture the flow regulator 32's cavities 40,52. The inlet and outlet valve recesses 198, 202 may be provided with alayer of one or more corrosion-resistant substances in any suitable way,such as those described above for the radial flow regulator 32's layerof corrosion-resistant substances.

The pump 190's inlet and outlet valves 134, 137, and its inlet andoutlet tubes 192, 194, may be assembled or bonded to its substrate 132in any suitable leak-proof way, such as those described above forassembling or bonding together the radial flow regulator 32's substrate34 and membrane 36.

MICROMACHINED ONE-WAY MEMBRANE VALVE 210 HAVING A RECTANGULAR FLEXUREAND A RING-SHAPED INLET VALVE SEAT (FIGS. 23-25): STRUCTURE

The first embodiment of the micromachined one-way membrane valve 210 isillustrated in FIGS. 23-25. The membrane valve 210 may comprise asubstrate 212, and a membrane 214.

The substrate 212 may have an inlet port 216; an inlet cavity 218; aninlet valve seat 220; and an outlet cavity 224.

Although a single inlet port 216 and a single inlet cavity 218 areillustrated, there may be more than one of each of these elements.

Although an inlet port 216 having a venturi-shaped configuration forbetter fluid flow is illustrated, it may have any other suitable shape,such as round or cylindrical. Although the inlet port 216 is illustratedas being co-axial with the inlet cavity 218, it may have any othersuitable spatial relationship with respect to the inlet cavity 218. Forexample, the inlet port 216 might be transverse to the inlet cavity 218,and enter the inlet cavity 218 from its side, rather from beneath.

Although an inlet cavity 218 having a circular or cylindricalconfiguration and a uniform depth is illustrated, it may have any othersuitable size and configuration, and a non-uniform depth. The inletcavity 218 may be used to define a clean outer perimeter for the inletport 216, particularly if the inlet port 216 is drilled with a laser.However, the inlet port 216 may be eliminated, and the inlet cavity 218may be extended downwardly so that it communicates directly with thesubstrate 212's bottom surface 213. Alternatively, the inlet cavity 218may be eliminated, and the inlet port 216 may be extended upwardly sothat it communicates directly with the substrate 212's top surface 242.

Although one rectangular outlet cavity 224 having a uniform depth isillustrated, there may be more than one outlet cavity 224, and each suchoutlet cavity may have any other suitable size, shape and depth; and itsdepth may not be uniform. Alternatively, the outlet cavity 224 may beeliminated, so that the inlet valve seat 220 may simply be all or partof those portions of the substrate 212's top surface 242 which underliethe flexure 228.

Although the inlet valve seat 220 is illustrated as having a ring-shapedconfiguration, it may have any other suitable configuration, such assquare or rectangular.

The membrane 214 may comprise a mounting portion 226 which is mounted tothe substrate 212; a flexure 228 which is not mounted to the substrate213, and which extends across the inlet valve seat 220; and a pair ofoutlet ports 230.

The substrate 212 and the membrane 214 may have any other suitable size,shape and thickness. Although the substrate 212 and the membrane 214 areillustrated as being of uniform thickness, they may have a non-uniformthickness.

Although a rectangular flexure 228 of uniform thickness is illustrated,the flexure 228 may have any other suitable shape, and its thickness maynot be uniform.

Although two rectangular outlet ports 230 are illustrated, there may befewer, or more, outlet ports 230, and each outlet port may have anysuitable shape.

Together, the substrate's inlet valve seat 220 and the membrane'sflexure 228 comprise an inlet valve 232. Preferably, the top of theinlet valve seat 220 and the top 242 of the rest of the substrate 212may be coplanar, so that when there is no positive driving pressuredifference (P) across the one-way membrane valve 210, the flexure 228lies flat across the top of the inlet valve seat 220.

Although only one inlet valve 232 is illustrated, there may be more thanone inlet valve 232. Although the inlet valve 232 is illustrated ashaving only flexure 228 and one inlet valve seat 220, each inlet valve232 may have more than one flexure 228 and more than one inlet valveseat 220.

By way of example, the one-way membrane valve 210 may have the followingphysical parameters. The one-way membrane valve 210 may be manufacturedon a square chip having sides about 3900 microns long. The substrate 212may be manufactured from 7740 Pyrex glass and have a maximum thicknessof about 0.5 mm. The inlet port 216 may have a minimum diameter of about50 microns, and a length of about 475 microns. The inlet cavity 218 mayhave a diameter of about 635 microns, and a depth of about 25 microns.The inlet valve seat 220 may have an outer diameter of about 1143microns, and an inner diameter of about 635 microns. The outlet cavitymay be a square having sides about 2900 microns long, and may have adepth of about 25 microns. The membrane 214 may be manufactured fromsilicon, and may have a thickness of about 9.0 microns. The outlet ports230 may each have a width of about 480 microns, and a length of about2900 microns. The flexure 228 may have a thickness of about 9.0 microns,a length of about 2900 microns, and a width of about 1940 microns.

The flow characteristics of this example one-way membrane valve 210 areillustrated in FIG. 29A.

MICROMACHINED ONE-WAY MEMBRANE VALVE 210 HAVING A RECTANGULAR FLEXUREAND A RING-SHAPED INLET VALVE SEAT (FIGS. 23-25): OPERATION AND THEORY

The valve 210 may be installed in its intended location of use in anysuitable way. Any suitable medication supply means may be used toconnect the one-way membrane valve 210's inlet port 216 to a source ofthe medication 12; and any suitable medication delivery means may beused to connect the one-way membrane valve 210's outlet ports 230 towhatever person, object or thing is to receive the medication 12 fromthe outlet ports 230.

During operation, as seen in FIGS. 24-25, if a positive driving pressuredifference (P) is applied across the one-way membrane valve 210, such asby pressurizing the source of the medication 12 with respect to theone-way membrane valve 210's outlet ports 230, the pressure of themedication 12 beneath the flexure 228 will cause the flexure 228 to bowaway from, and unseat from, the inlet valve seat 220. This will permitthe medication 12 to flow in through the inlet port 216, and the inletcavity 218; to flow radially outwardly through the valve gap 234 betweenthe inlet valve seat 220 and the flexure 228; and to flow out throughthe outlet ports 224.

On the other hand, if a negative driving pressure difference (P) isapplied across the one-way membrane valve 210, such as by pressurizingthe medication 12 adjacent to the top of the flexure 228 with respect tothe inlet port 216, the pressure of the medication 12 on top of theflexure 228 will drive the flexure 228 towards, and seat it against, theinlet valve seat 220. This will prevent any back flow of the medication12 through the inlet port 216.

Referring now to FIG. 29A, the six circular data points 215 are for themeasured flow rate (Q), in microliters per second, of the exampleone-way membrane valve 210, whose physical parameters were set forthabove; as a function of the driving pressure difference (P) across theone-way membrane valve 210, in mm Hg. The medication 12 was distilledwater. The solid line 217 shown in FIG. 29A is a data-fit line for thedata points 215.

When the above example one-way membrane valve 210, whose physicalparameters were set forth above, was tested in a reverse flow condition,the leak rate at about 150.0 mm Hg of pressure was less than about 0.2microliters/second, which corresponds to a forward-to-reverse flow ratioin excess of 100:1.

It has been discovered that one of the valve 210's notable features maybe that, because the flexure 228 may be so thin and flexible, it mayconform unusually well to the valve seat 220's top surface 241, despitethe normal, very small variations in the flatness of the flexure 228'sbottom surface 243, and in the inlet valve seat 220's top surface 241.Such conformity is desirable, since it results in reducing, if noteliminating, any back flow of the medication 12 through the valve 210when it is subjected to a negative driving pressure difference (P). Inaddition, such conformity is desirable because it enables the forwardopening characteristics of the one-way membrane valve 210 to be "tuned".

Another of the valve 210's notable features may be the fact that bothends of its flexure 228 may be anchored to the substrate 212, as is seenFIGS. 23 and 24. Such anchoring of both ends of the flexure 228 offersnumerous advantages.

For example, it has been discovered that anchoring both ends of theflexure 228 may result a flexure 228 having superior flatness (under azero or negative driving pressure difference (P) across the valve 210),and thus having superior conformity to the inlet valve seat 220's topsurface 241, as compared to a flexure 228 which is cantilevered, i.e.,which is anchored at only one of its ends. This is because a flexure 228which is anchored at both of its ends is more geometrically constrained,as compared to a cantilevered flexure 228, and thus its side edges areless likely to curl. Such flatness and conformity of the flexure 228 isdesirable because it results in better sealing between the flexure 228and the inlet valve seat 220's top surface 241; which, in turn, mayreduce, if not eliminate, any back flow of the medication 12 through thevalve 210 when it is subjected to negative driving pressure differences(P). In addition, such conformity is desirable because it enables theforward opening characteristics of the one-way membrane valve 210 to be"tuned".

It has been further discovered that anchoring both ends of the flexure228 enables the flexure 228 to be "preconformed" to the inlet valve seat220's top surface 241. By "preconformed", it is meant that the flexure228 and the inlet valve seat 220's top surface 241 are in intimatecontact when the one-way membrane valve 210 is at its designed operatingtemperature, and when there is a zero driving pressure difference (P)across the one-way membrane valve 210. Such preconforming results inreducing, or even eliminating, any back flow of the medication 12through the valve 210 when it is subjected to a negative drivingpressure difference (P). In addition, such preconforming is desirablebecause it enables the forward opening characteristics of the one-waymembrane valve 210 to be "tuned".

It has also been discovered that a flexure 228 which is anchored at bothends may be used without a rigid center boss, such as the boss which isdisclosed in FIG. 1 of the article entitled "A Piezoelectric MicropumpBased On Micromachining Of Silicon by H. T. G. Van Lintel et al.,Sensors and Actuators, 15 (1988) 153-167. It has been discovered that aflexure 228 which does not have such a rigid center boss is moreflexible than one which has such a boss, and thus is more conformable tothe inlet valve seat 220's top surface 228. Such conformity isdesirable, since it results in reducing, if not eliminating, any backflow of the medication 12 through the valve 210 when it is subjected toa negative driving pressure difference (P). In addition, such conformityis desirable because it enables the forward opening characteristics ofthe one-way membrane valve 210 to be "tuned". It has also beendiscovered that such increased flexibility of the flexure 228 isdesirable since it may be translated into either a smaller one-waymembrane valve 210, or a one-way membrane valve 210 which has a lowerforward pressure drop.

It has also been discovered that a flexure 228 which is anchored at bothends may be prestressed, i.e., that the flexure 228 may be under tensionwhen the one-way membrane valve 210 is at its designed operatingtemperature, and when there is a zero driving pressure difference (P)across the one-way membrane valve 210. Such prestressing of the flexure228 offers numerous advantages. For example, under a supposedly zerodriving pressure difference (P) across the one-way membrane valve 210,the valve 210 may "bleed" the medication 12. It has been discovered thatprestressing the flexure 228 may at least partially, if not totally,eliminate this potential problem because, due to the tension in theprestressed flexure 228, it takes a small, but not an insignificant,positive driving pressure difference across the one-way membrane valve210, to cause the prestressed flexure 228 to unseat from the valve seat220. Thus, the prestressed flexure 228 is much less likely to bleed themedication 12 under a supposedly zero driving pressure difference (P)across the one-way membrane valve 210. In addition, such a prestressedflexure 228 results in reducing, or even eliminating, any back flow ofthe medication 12 through the valve 210 when it is subjected to anegative driving pressure difference (P). Further, such prestressing ofthe flexure 228 enables the forward opening characteristics of theone-way membrane valve 210 to be "tuned". This is because as the amountof the tension in the prestressed flexure 228 is increased, the minimumpositive driving pressure difference (P) across the one-way membranevalve 210 which is needed to unseat the flexure 228 from the valve seat220 also increases (and vice versa). In addition, as the amount oftension in the prestressed flexure 228 is increased, the size of theinlet valve gap 234, and the flow rate (Q) of the medication 12 throughthe one-way membrane valve 210, for any given driving pressuredifference (P) across the one-way membrane valve 210, will decrease (andvice versa).

It has also been discovered that, as a result of all of the forgoingconsiderations, the valve 210 offers the attractive advantages ofincreased uniformity and increased yield when mass produced, as comparedto a valve 210 which has a less flexible flexure 228, which has acantilevered flexure, or which has a rigid center boss.

It should be noted that, because the inlet and the outlet ports 216, 230are located on opposite sides the one-way membrane valve 210, the valve210 may be used either as a one-way inlet valve 210, or as a one-wayoutlet valve 210, merely by turning it over. For example, referring nowto FIG. 20, the valve 210 may be substituted for the one-way inlet valve134, 300 by mounting the valve 210 with its membrane 214 towards thepump 190's substrate 132; and the valve 210 may be substituted for theone-way outlet valve 137, 300 by mounting the valve 210 with itssubstrate 212 towards the pump 190's substrate 132.

It should also be noted that, if the valve 210 were mounted in itsintended location of use so that the top surface of the flexure 228 wasin close proximity to a flat surface, and so that at least some of themedication 12 exiting from one or more of the outlet ports 230 had topass through the gap between the flat surface and the top surface of theflexure 228, then the flexure 228 and the flat surface would, in effect,operate as a flow regulator similar to the radial flow regulator 32 ofFIGS. 1-2, to regulate the flow of the medication 12 from the valve 210.In such a case, the flat surface would act as a regulator seat, similarto the regulator seat 42; the flexure 228 would act as a regulatorflexure, similar to the regulator flexure 36; and the gap between theflexure 228 and the flat surface would act as a regulator gap, similarto the regulator gap 48.

A mathematical model for the behavior of the one-way valve 210 may besimilar to the mathematical model set forth below for the one-way valve240.

From the disclosures in this document, it is seen that it is possible toselectively design a one-way membrane valve 210 having any particulardesired forward flow rate (Q) of the medication 12 as a function of thedriving pressure difference (P) across the one-way membrane valve 210.This may be done by selectively adjusting one or more of the pertinentparameters, such as: (a) the stiffness, elasticity, resiliency, length,width, thickness, shape, cross-sectional configuration, and amount ofprestressing of the flexure 228; (b) the number, size and shape of theinlet port 216, the inlet cavity 218, the inlet valve seat 220, theoutlet cavity 224, and the outlet ports 224; and (c) the drivingpressure difference (P) across the one-way membrane valve 210.

MICROMACHINED ONE-WAY MEMBRANE VALVE 210 HAVING A RECTANGULAR FLEXUREAND A RING-SHAPED INLET VALVE SEAT (FIGS. 23-25): MANUFACTURE

The one-way membrane valve 210's substrate 212 may be manufactured fromany suitable strong, durable material which is compatible with themedication 12, and in which the inlet port 216, the inlet cavity 218 andthe outlet cavity 224 may be manufactured in any suitable way, such asby using any suitable etching, molding, stamping and machining process.Such a machining process may include the use of physical tools, such asa drill or saw; the use of electromagnetic energy, such as a laser; andthe use of a water jet.

The membrane 214 may be manufactured from any suitable strong, durable,flexible, material which is compatible with the medication 12, and inwhich the outlet ports 230 may be manufactured in any suitable way, suchas by using any suitable etching, molding, stamping and machiningprocess. Such a machining process may include the use of physical tools,such as a drill or saw; the use of electromagnetic energy, such as alaser; and the use of a water jet.

If the one-way membrane valve 210 is intended to be used with amedication 12 which is to be supplied to a human or an animal, then anypart of the one-way membrane valve 210 which is exposed to themedication 12 should be manufactured from, and assembled or bonded with,non-toxic materials. Alternatively, any toxic material which is used tomanufacture the one-way membrane valve 210, and which is exposed to themedication 12 during use of the one-way valve 210 may be provided withany suitable non-toxic coating which is compatible with the medication12.

Suitable materials for the substrate 212 and the membrane 214 may bemetals (such as titanium), glasses, ceramics, plastics, polymers (suchas polyimides), elements (such as silicon), various chemical compounds(such as sapphire, and mica), and various composite materials.

The substrate 212 and the membrane 214 may be assembled together in anysuitable leak-proof way. Alternatively, the substrate 212 and themembrane 214 may be bonded together in any suitable leak-proof way, suchas by anodically bonding them together; such as by fusing them together(as by the use of heat or ultrasonic welding); and such as by using anysuitable bonding materials, such as adhesive, glue, epoxy, solvents,glass solder, and metal solder.

Anodically bonding the substrate 212 and the membrane 214 together maybe preferable for reasons which are the same as, or at least similar to,the reasons set forth above for anodically bonding the radial flowregulator 32's substrate 34 and membrane 36 together.

It has also been discovered that anodically bonding the substrate 212and membrane 214 together may be desirable for at least two additionalreasons. First, it has been discovered that the elevated temperatureswhich are used during the anodic bonding process may be used toautomatically prestress the flexure 228. This will be discussed in moredetail below.

Second, it has also been discovered that the elevated temperatures andvoltages used during the anodic bonding process may be used toautomatically cause the inlet valve seat 220 and the flexure 228 toconform to each other, thereby resulting in a better seal therebetweenthan might otherwise be the case. This is because such elevatedtemperatures during the anodic bonding process tend to soften thesubstrate 212, while such elevated voltages during the anodic bondingprocess tend to draw the softened substrate 212 and flexure 214 tightlytogether, thereby physically deforming the flexure 228 and the inletvalve seat 220 enough to "smooth out" to some degree any microscopicirregularities which may be present on the mating surfaces of theflexure 228 and the inlet valve seat 220.

One example of how the one-way membrane valve 210 may be manufacturedwill now be given. The starting point may be a 76.2 mm diameter wafer ofCorning 7740 Pyrex glass, which will form the one-way membrane valve210's substrate 212.

The inlet cavity 218 and the outlet cavity 224 may be manufactured inthe substrate 212 in any suitable way. One suitable way may be to use anetching process which is the same as, or at least similar to, that usedto form the radial flow regulator 32's inlet channels 38, inlet cavity40, regulator seat 42 and outlet port 54 of FIGS. 1-2, except for thosedifferences, if any, which will be made apparent by an examination ofall of the Figures and disclosures in this document.

The inlet port 216 may then be formed in the substrate 212 in anysuitable way. The structure, operation, theory and manufacture of theone-way membrane valve 210's inlet port 216 may be the same as, or atleast similar to, those of the radial flow regulator 32's outlet port 54of FIGS. 1-2, except for those differences, if any, which will be madeapparent by an examination of all of the Figures and disclosures in thisdocument.

Next, a nominal layer of one or more corrosion-resistant materialsubstances may then be deposited onto all of the surfaces of the inletport 216, the inlet cavity 218, the inlet valve seat 220, and the outletcavity 224. The structure, operation, theory and manufacture of such alayer of one or more corrosion-resistant substances for the one-waymembrane valve 210 may be the same as, or at least similar to, those ofthe layer of one or more corrosion-resistant substances for the radialflow regulator 32 of FIGS. 1-2, except for those differences, if any,which will be made apparent by an examination of all of the Figures anddisclosures in this document.

It has been discovered that such a layer of corrosion-resistantsubstance(s) may serve at least one important function, in addition toits corrosion-resistant function, if the membrane 214 is anodicallybonded to the substrate 212. That is, the layer of corrosion-resistantsubstance(s) may prevent the flexure 228 from being bonded to the inletvalve seat 220 during the anodic bonding process.

The membrane 214, with its outlet ports 230, may be manufactured from asilicon wafer, and secured to the glass wafer (which is the substrate212) in any suitable way. The structure, operation, theory andmanufacture of the one-way membrane valve 210's membrane 214, with itsoutlet ports 230, and the securing of the membrane 214 to its substrate212 is the same as, or at least similar to, the manufacturing of thelinear flow regulator 80's membrane 84, with its inlet port 88, and thesecuring of its membrane 84 to its substrate 86, except for thosedifferences, if any, which will be made apparent by an examination ofall of the Figures and disclosures in this document.

If it is desired to intentionally prestress the flexure 228, the flexure228 may be prestressed in any suitable way. One suitable way may be toselect materials for the substrate 212 and the membrane 214 which havedifferent thermal expansion coefficients, such as a wafer of 7740 Pyrexglass for the substrate 212 and a wafer of silicon for the membrane 214,for example. Then, after the glass wafer (the substrate 212) has beenetched, and the boron-doped layer of the silicon wafer has been etched,the glass and silicon wafers may be heated (or cooled) to a temperaturewhich is higher than (or lower than) the designed operating temperaturerange of the one-way membrane valve 210. The glass and silicon wafersmay then be secured together at that higher (or lower) temperature, inany suitable way. Then, when the one-way membrane valve 210 is returnedto its designed operating temperature range, and the manufacture of themembrane 214, with its outlet ports 230, has been completed, thedifference in the thermal expansion coefficients of the substrate 212and the membrane 214 will cause the flexure 228 to be prestressed to thedesired amount.

For example, if, as mentioned above, the substrate 212 and the membrane214 were selected to be manufactured from 7740 Pyrex glass and silicon,respectively; and the substrate 212 and the membrane 214 may be bondedtogether by using anodic bonding at a temperature higher than theone-way membrane valve 210's designed operating temperature range, suchas from about 300° C. to about 520° C.

The manufacture of only one one-way membrane valve 210 was describedabove. However, it will be appreciated that on any pair of glass andsilicon wafers the substrates 212 and the membranes 214 for a largenumber of one-way membrane valves 210 could be manufacturedsimultaneously in a manner similar to that described above. If such isthe case, an array of substrates 212 may be simultaneously etched in theglass wafer; their inlet ports 216 may be drilled, and the layer of oneor more corrosion-resistant substances may be applied to the substrates212. Then an array of outlet ports 230 may be simultaneously etched inthe silicon wafer. Next, the silicon and glass wafers for the substrates212 and the membranes 214 may be aligned and bonded together. Then, allof the membranes 214 may be formed simultaneously by grinding andetching the silicon wafer to its desired final thickness. Thesiliconglass substrate 212membrane 214 sandwich may then be divided byany suitable means (such as dicing) into individual chips, each chipbearing at least one one-way membrane valve 210.

One of the advantages of using etching and anodic bonding processes tomanufacture the one-way membrane valve 210, is that such processesenable high quality, very reliable, one-way membrane valves 210 to bemass produced in great numbers at a cost so low that the one-waymembrane valves 210 may be considered to be disposable. Other advantagesof using an anodic bonding process to bond the substrate 212 and themembrane 214 together were described in detail above, i.e., to prestressthe flexure 228, and to conform the inlet valve seat 220 and the flexure228 to each other, for a better seal therebetween.

Further, it should also be noted that the one-way membrane valve 210 isstunning in its simplicity since it has only two basic parts, i.e. itssubstrate 212 and its membrane 214; and since only one of its parts is amoving part, i.e., its flexure 228, which merely bows during operationof the one-way membrane valve 210. Further, because the raw materialsfrom which the one-way membrane valve 210 may be manufactured may bevery inexpensive, such as glass and silicon, the cost of the one-waymembrane valve 210 may held to a very low level.

MICROMACHINED ONE-WAY MEMBRANE VALVE 240 HAVING A RECTANGULAR FLEXUREAND A RECTANGULAR INLET VALVE SEAT (FIGS. 26-29): STRUCTURE

The micromachined one-way membrane valve 240 which is illustrated inFIGS. 26-28 is the same as, or at least similar to, the micromachinedone-way membrane valve 210 of FIGS. 23-25 in its structure, except forthose differences which will be made apparent by an examination of allof the Figures and all of the disclosures in this document. Accordingly,the respective parts of the one-way membrane valve 240 have been giventhe same reference numerals as the corresponding parts of the one-waymembrane valve 210 of FIGS. 23-25, for clarity and simplicity.

Turning now to FIGS. 26-28, although a single inlet port 216 and asingle inlet cavity 218 are illustrated, there may be more than one ofeach of these elements.

Although a rectangular inlet port 216, which is co-planar with the inletcavity 218, is illustrated, the inlet port 216 may have any othersuitable size and shape. In addition, the inlet port 216 may have anyother suitable spatial relationship with respect to the inlet cavity218. For example, the inlet port 216 may be transverse to the inletcavity 218, and enter the inlet cavity 218 from below, rather than fromone side.

Although a rectangular inlet cavity 218 having a uniform depth isillustrated, it may have any other suitable size and shape, and may havea non-uniform depth. In addition, the inlet port 216 may be eliminated,and the inlet cavity 218 may be extended so that it communicatesdirectly with the substrate 212's outer surface and performs thefunctions of the inlet port 216. Alternatively, the inlet cavity 218 maybe eliminated, and the inlet port 216 may be extended so that itperforms the functions of the inlet cavity 218.

Although no outlet cavity 224 is illustrated, the one-way membrane valve240 may be provided with an outlet cavity 224 which is the same as, orwhich is similar to, the one-way membrane valve 230's outlet cavity 224.

Although a pair of parallel, rectangular inlet valve seats 220 areillustrated, there may be fewer, or more, inlet valve seats 220, andeach inlet valve seat 220 may have any other suitable size and shape.

By way of example, the one-way membrane valve 240 may have the followingphysical parameters. The substrate 212 may be made from 7740 Pyrex glassand have a thickness of about 0.5 mm. The inlet port 216 may have awidth of about 0.5 mm and a depth of about 25 microns. The inlet cavity218 may have a length of about 3.18 mm, a width of about 0.5 mm, and adepth of about 25 microns. Each inlet valve seat 220 may have a lengthof about 3.18 mm and a width of about 0.25 mm. The membrane 214 may bemade from silicon, and may have a thickness of about 25.0 microns. Theoutlet ports 230 may each have a width of about 0.5 mm, and a length ofabout 3.18 mm. The flexure 228 may be about 25.0 microns thick, about3.18 mm long, and about 1.0 mm wide.

The flow characteristics of this example one-way membrane valve 240 areillustrated in FIG. 29B.

MICROMACHINED ONE-WAY MEMBRANE VALVE 240 HAVING A RECTANGULAR FLEXUREAND A RECTANGULAR INLET VALVE 8EAT (FIGS. 26-29): OPERATION AND THEORY

The micromachined one-way membrane valve 240 which is illustrated inFIGS. 26-28 is the same as, or at least similar to, the micromachinedone-way membrane valve 210 of FIGS. 23-25 in its operation and theory,except for those differences which will be made apparent by anexamination of all of the Figures and all of the disclosures in thisdocument.

During operation, as seen in FIGS. 27-28, if a positive driving pressuredifference (P) is applied across the one-way membrane valve 240, such asby pressurizing the source of the medication 12 with respect to theone-way membrane valve 240's outlet ports 230, the pressure of themedication 12 beneath the flexure 228 will cause the flexure 228 to bowaway from, and unseat from, the inlet valve seats 220. This will permitthe medication 12 to flow in through the inlet port 216, and the inletcavity 218; to flow outwardly through the valve gap 234 between thevalve seats 220 and the flexure 228; and to flow out through the outletports 224.

On the other hand, if a negative driving pressure difference (P) isapplied across the one-way membrane valve 240, such as by pressurizingthe medication 12 adjacent to the top of the flexure 228 with respect tothe inlet port 216, the pressure of the medication 12 on top of theflexure 228 will drive the flexure 228 towards, and seat it against, theinlet valve seats 220. This will prevent any back flow of the medication12 of the inlet port 216.

Referring now to FIG. 29B, the eleven square data points 244 are for themeasured flow rate (Q), in microliters per second, of the exampleone-way membrane valve 240, whose physical parameters were set forthabove; as a function of the driving pressure difference (P) across theone-way membrane valve 210, in mm Hg. The medication 12 was distilledwater at about 23° C. The solid line 246 shown in FIG. 29B is a plot ofthe predicted performance of the example one-way membrane valve 240,whose physical parameters were set forth above, under a performancetheory which will be discussed below.

When the above example one-way membrane valve 240, whose physicalparameters were set forth above, was tested in a reverse flow condition,the leak rate at 200 mm Hg was less than 0.00145 microlitersminute,which corresponds to a forward-to-reverse flow ratio in excess of40.100:1, even if the designed forward flow rate was only about 1.0microliter per second.

It should be noted that, if the valve 240 were mounted in its intendedlocation of use so that the top surface of the flexure 228 was in closeproximity to a flat surface, and so that at least some of the medication12 exiting from one or more of the outlet ports 230 had to pass throughthe gap between the flat surface and the top surface of the flexure 228,then the flexure 228 and the flat surface would, in effect, operate as aflow regulator similar to the radial flow regulator 32 of FIGS. 1-2, toregulate the flow of the medication 12 from the valve 210. In such acase, the flat surface would act as a regulator seat, similar to theregulator seat 42; the flexure 228 would act as a regulator flexure,similar to the regulator flexure 36; and the gap between the flexure 228and the flat surface would act as a regulator gap, similar to theregulator gap 48.

A mathematical model for the valve 240 will now be given. To predict therelationship between the flow rate (Q) of the medication 12 and thedriving pressure difference (P) for the valve 240, the two dimensionalcoordinate system shown in FIG. 29C may be used. The origin (0,0) may beplaced on the longitudinal axis of the inlet cavity 218, halfway alongthe flexure 228, in the plane of the top surface of the inlet valveseats 220.

It is assumed that the flexure 228 is curved only in the X-Y plane; thatthe flexure 228 is flat perpendicular to the X-Y plane; that all of thedriving pressure difference (P) is dropped across the valve seats 220;that all other portions of the valve 240 have fluid pressures which areconstant; and that each valve seat 220 is narrow compared to the totalwidth of the flexure 228, i.e., has a width ratio of about 1:5, or less.

If movement of the flexure 228 is represented by the one-dimensionaldeflection of a thin, rectangular slab element which is subjected to aconstant driving pressure difference (P) across its surface, within thearea encompassed by the perimeter of the valve seat 220, and which issecured to the substrate 212 at both of its ends, then its deflection isgiven by above Equation 5, where Y₀ is the maximum deflection of theflexure 228 at x=0. The centerline deflection of the flexure 228 isgiven by above equation 5A, where the pressure difference (p_(s) -p) inthat equation is now replaced by the pressure drop across the inletvalve seat 220, ΔP.

To calculate the total flow rate (Q) of the medication 12 correspondingto this pressure drop, a differential fluid slice (dx) wide is usedwhich spans the inlet valve gap 234. If the bowing or deflection of theflexure 228 is very slight, then it may be assumed that this local fluidslice has a negligible shear along its sides and is dominated by viscousdrag at top and bottom. With this assumption, it may be found that thetotal flow rate (Q) per valve seat 220 is given by: ##EQU14## where s isthe width of the inlet valve seat 220 and μ is the viscosity of themedication 12.

A similar approach may be used to calculate the flow characteristics ofa valve with a circular valve seat (such as the valve 210), or a valvelike the valve 210, but which has a square or rectangular valve seat220. This would entail developing a deflection equation corresponding tothe flexure 228's new pressure loading, as defined by the outline of itsparticular valve seat 220, and then integrating the above integralequation 8 around the perimeter of the inlet valve seat 220 to determinethe total flow rate (Q) of the medication 12.

From the disclosures in this document, it is seen that it is possible toselectively design a one-way membrane valve 240 having any particulardesired forward flow rate (Q) of the medication 12 as a function of thedriving pressure difference (P) across the one-way membrane valve 240.This may be done by selectively adjusting one or more of the pertinentparameters, such as: (a) the stiffness, elasticity, resiliency, length,width, thickness, shape, cross-sectional configuration, and amount ofprestressing of the flexure 228; (b) the number, size and shape of theinlet port 216, the inlet cavity 218, the inlet valve seat 220, theoutlet cavity 224, and the outlet ports 224; and (c) the drivingpressure difference (P) across the one-way membrane valve 210.

MICROMACHINED ONE-WAY MEMBRANE VALVE 240 HAVING A RECTANGULAR FLEXUREAND A RECTANGULAR INLET VALVE SEAT (FIGS. 26-29): MANUFACTURE

The micromachined one-way membrane valve 240 which is illustrated inFIGS. 26-28 is the same as, or at least similar to, the micromachinedone-way membrane valve 210 of FIGS. 23-25 in its manufacture, except forthose differences which will be made apparent by an examination of allof the Figures and all of the disclosures in this document.

The inlet port 216 and the inlet cavity 218 may be manufactured in thesubstrate 212 in any suitable way. One suitable way may besimultaneously etch them into the substrate 212 by using an etchingprocess which is the same as, or at least similar to, that used to formthe radial flow regulator 32's inlet channels 38, inlet cavity 40,regulator seat 42 and outlet port 54 of FIGS. 1-2, except for thosedifferences, if any, which will be made apparent by an examination ofall of the Figures and disclosures in this document.

MICROMACHINED ONE-WAY MEMBRANE VALVE 300 HAVING A CIRCULAR FLEXURE AND ACIRCULAR INLET VALVE SEAT (FIGS. 30-32): STRUCTURE

The third embodiment of the micromachined one-way membrane valve 300 ofthe present invention is illustrated in FIGS. 30-31. The one-waymembrane valve 300 may comprise a substrate 302 and a membrane 304.

The substrate 302 may have a pair of inlet ports 306; an inlet cavity308; and an inlet valve seat 310.

Although a pair of inlet ports 306, having a venturi-shape for betterfluid flow therethrough, are illustrated, there may be fewer or moreinlet ports 306, and each inlet port 306 may have any other suitablesize and shape. For example, the one-way membrane valves 300 illustratedin FIG. 21 have four inlet ports 306.

Although only one ring-shaped inlet cavity 308 is illustrated, there maybe more than one inlet cavity 308, and each inlet cavity 308 may haveany other suitable size and shape.

Although the inlet valve seat 310 is illustrated as being cylindrical,it may have any other suitable size and shape. Although the inlet valveseat 310's top surface 318 is preferably at least about 2.0 micronshigher than the regulator 302's top surface 320, the inlet valve seatmay be about the same height as, or lower than, the regulator 302's topsurface 320.

The membrane 304 may have a mounting portion 312, which is secured tothe substrate 302's top surface 320 outside of the inlet cavity 308; itmay have a flexure portion 314, which is not secured to the substrate302, and which extends over the inlet cavity 308 and over part of theinlet valve seat 310; and it may have an outlet port 316, which alsooverlies part of the inlet valve seat 310. Although the outlet port 316is illustrated as being circular, it may have any other suitable sizeand shape.

By way of example, the one-way membrane valve 300 may have the followingphysical parameters. The one-way membrane valve 300 may be a squarehaving sides about 5 mm long. The substrate 212 may be made from 7740Pyrex glass and have a maximum thickness of about 0.5 mm. The inletports 306 may have a minimum diameter of about 100 microns and a lengthof about 475 microns. The inlet cavity 308 may have a maximum diameterof about 4.3 mm, and a depth of about 25 microns; the inlet valve seatmay have a diameter of about 890 microns, and a height of about 27-29microns. The membrane 304 may be made from epitaxial silicon, and mayhave a thickness of about 25 microns. The flexure 314 may have an outerdiameter of about 4.3 mm. The flexure 314's outlet port 316 may have adiameter of about 500 microns.

MICROMACHINED ONE-WAY MEMBRANE VALVE 300 HAVING A CIRCULAR FLEXURE AND ACIRCULAR INLET VALVE SEAT (FIGS. 30-32): OPERATION AND THEORY

The one-way membrane valve 300 may be installed in its intended locationof use in any suitable way. Any suitable medication supply means may beused to connect the one-way membrane valve 300's inlet ports 306 to asource of the medication 12; and any suitable medication delivery meansmay be used to connect the one-way membrane valve 300's outlet port 316to whatever person, object or thing is to receive the medication 12 fromthe outlet port 316.

During operation, as seen in FIG. 31, if a positive driving pressuredifference (P) is applied across the one-way membrane valve 300, such asby pressurizing the source of the medication 12 with respect to theone-way membrane valve 300's outlet port 316, the pressure of themedication 12 beneath the flexure 314 will cause the flexure 314 to bowaway from, and unseat from, the inlet valve seat 310. This will permitthe medication 12 to flow in through the inlet ports 306, and the inletcavity 308; to flow radially inwardly through the inlet valve gap 321between the inlet valve seat 310 and the flexure 314; and to flow outthrough the outlet port 316.

On the other hand, if a negative driving pressure difference (P) isapplied across the one-way membrane valve 300, such as by pressurizingthe medication 12 adjacent to the top of the flexure 314 with respect tothe inlet ports 306, the pressure of the medication 12 on top of theflexure 314 will drive the flexure 314 towards, and seat it against, theinlet valve seat 310. This will prevent any back flow of the medication12 through the inlet ports 306.

It has been discovered that if the valve 300 is manufactured so that theinlet valve seat 310's top surface 318 is coplanar with the substrate302's top surface 320, then the normal, very small variations in theflatness of the inlet valve seat 310's top surface 318, and in theflatness of the flexure 314's bottom surface 322 (hereinafter termed"co-planar flatness variations"), may give rise to at least fourpotential problems.

However, it has also been discovered that if the inlet valve seat 310 ismade so that its top surface 318 is slightly higher than the substrate302's top surface 320 (on the order of at least about 2 microns, forexample), then the flexure 314 will be prestressed. By "prestressed", itis meant that the height difference between the top surface 318 of theinlet valve seat 310 and the top surface 320 of the substrate 302 causesthe flexure 314 to be pressed against the inlet valve seat 220 when theone-way membrane valve 310 is at its designed operating temperature, andwhen there is a zero driving pressure difference (P) across the one-waymembrane valve 300. It has also been discovered that the amount of suchprestressing of the flexure 314 is a function of such height difference,with the amount of such prestressing of the flexure 314 increasing asthe height difference increases (and vice versa).

It has been discovered that by prestressing the flexure 314, all four ofthe potential problems caused by co-planar flatness variations may be atleast partially, or even completely, eliminated.

The first potential problem caused by such co-planar flatness variationsis that there may be undesirable back flow of the medication 12 throughthe valve 300 when there is a negative driving pressure difference (P)across the one-way membrane valve 300. Such back flow of the medication12 may render the one-way membrane valve 300 unfit for use where suchback flow cannot be tolerated in the particular intended use for theone-way membrane valve 300. For example, if the one-way membrane valve300 was to be used in a medication delivery apparatus, such back flowmight permit blood, or other body fluids, to flow back into the one-waymembrane valve 300, and clog it.

However, it has been discovered that prestressing the flexure 314 mayreduce, or even eliminate, any back flow of the medication 12 throughthe one-way membrane valve 300 when there is a negative (reverse)driving pressure difference (P) across the one-way membrane valve 300.This is because prestressing the flexure 314 may physically deform theflexure 314 and the inlet valve seat 310 enough to "smooth out" to somedegree any microscopic irregularities which may be present on the matingsurfaces of the flexure 314 and the inlet valve seat 310; therebyimproving the conformity, and thus the sealing, between the flexure 314and the inlet valve seat 310. Such improved conformity and sealingbetween the flexure 314 and the inlet valve seat 310 may greatly reduce,if not eliminate, any back flow of the medication 12 when there is anegative (reverse) driving pressure difference (P) across the one-waymembrane valve 300.

In addition, it has also been discovered that prestressing the flexure314 may reduce, or even eliminate, any back flow of the medication 12through the one-way membrane valve 300 for the additional reason thatthe prestressed flexure 314 may tend to automatically seat against theinlet valve seat 310 when there is still a small positive drivingpressure difference (P) across the one-way membrane valve 300. Thus, itis very unlikely that there may be any back flow of the medication 12through the one-way membrane valve 300 as the driving pressuredifference (P) is changing from positive to negative.

The second potential problem caused by such co-planar flatnessvariations is that the forward flow rate (Q) of the medication 12through the one-way membrane valve 300, as a function of the drivingpressure difference (P) of the medication 12 across the one-way membranevalve 300, may differ from valve 300 to valve 300, even if a group ofvalves 300 is supposedly manufactured to have identical physicalparameters. Such differing forward flow characteristics may make certainone-way membrane valves 300 defective for their intended use, or mayincrease the cost of the one-way membrane valves 300 because each onemust be tested in order to determine its actual forward flow rate (Q)characteristic curve. However, it has been discovered that prestressingthe flexures 314 may at least partially, if not totally, eliminate thispotential problem by making all of the one-way membrane valves 300 whichare manufactured identically to have more nearly identical forward flowrates (Q) of the medication 12, as a function of the driving pressuredifference (P) of the medication 12 across the one-way membrane valves300.

The third potential problem caused by such co-planar flatness variationsis that under a supposedly zero driving pressure difference (P) acrossthe one-way membrane valve 300, the valve 300 may "bleed" the medication12. It has been discovered that prestressing the flexures 314 may atleast partially, if not totally, eliminate this potential problembecause, due to the tension in the prestressed flexure 314, it takes asmall, but not an insignificant, positive driving pressure differenceacross the one-way membrane valve 300, to cause the prestressed flexure314 to unseat from the valve seat 300. Thus, the prestressed flexure 314is much less likely to bleed the medication 12 under a supposedly zerodriving pressure difference (P) across the one-way membrane valve 300.

The fourth potential problem caused by such co-planar flatnessvariations is that it may be difficult, if not impossible to accurately"tune" the forward opening characteristics of the one-way membrane valve300. However, it has been discovered that prestressing the flexure 314may at least partially, if not totally, eliminate this potential problembecause as the amount of the tension in the prestressed flexure 314 isincreased, the minimum positive driving pressure difference (P) acrossthe one-way membrane valve 300 which is needed to unseat the flexure 314from the valve seat 310 also increases (and vice versa). In addition, asthe amount of tension in the prestressed flexure 314 is increased, thesize of the inlet valve gap 321, and the flow rate (Q) of the medication12 through the one-way membrane valve 300, for any given drivingpressure difference (P) across the one-way membrane valve 300, willdecrease (and vice versa). Thus, these factors make it clear that theforward opening characteristics of the one-way membrane valve 300 may be"tuned" by selecting the amount of the tension by which the flexure 314is prestressed.

It has been further discovered that, as a result of all of the forgoing;such prestressing of the flexure 314 results in a yield approaching100%, regarding the number of useable one-way membrane valves 300 whichare obtained during the manufacture of the one-way membrane valves 300.On the other hand, if the flexure 314 is not prestressed, then as manyas about 50%-75% of the valves 300 may be unusable, primarily because ofbuckling of the flexure 314, due to compressive loading, rather thantensile loading, on the flexure 314. Such buckling of the flexure 314may render the valve 300 unusable, since it may "bleed" under anominally zero driving pressure difference (P) across the valve 300, andsince the valve 300 may leak when subjected to a negative drivingpressure difference (P).

However, even though it may be desirable that the inlet valve seat's topsurface 318 is higher than the top surface 320 of the rest of thesubstrate 302, so that the flexure 310 may be prestressed, such a heightdifference may interfere with properly securing the membrane 304'smounting portion 312 to the substrate's top surface 320.

Nevertheless, it has been discovered that if suitable materials areselected for the substrate 302 and the membrane 304; if the membrane 304is formed from a wafer of material which is not reduced to its finalthickness until after the substrate 302 and the membrane 304 are securedtogether; and if the ratio of the inlet cavity 308's maximum diameter tothe inlet valve seat 310's height above the inlet cavity 308's bottom328 is appropriately selected, then anodic bonding may be used tosuccessfully secure the membrane 304 to the substrate 302, despite sucha height difference between the top surfaces 318, 320 of the inlet valveseat 310 and the substrate 302.

This is apparently because at the elevated bonding temperatures usedduring the anodic bonding, the substrate 302 may be relatively elastic,while the membrane 304's wafer may be relatively stiff, or non-elastic.This may permit the relatively stiff membrane 304's wafer to elasticallycompress the inlet valve seat 310, due to the electrostatic forces thatpull the substrate 302 and the membrane 304's wafer together during theanodic bonding process. Then, after the anodic bonding process iscomplete, and after the membrane 304's wafer has been reduced to itsfinal thickness, the compressed inlet valve seat 310 will rebound to itsoriginal, uncompressed condition, thereby automatically restoring thedesired height difference between the top surfaces 318, 320 of the inletvalve seat 310 and the substrate 302. This final result may also occur,of course, if both of the wafers for the substrate 302 and the membrane304 elastically deform during the anodic bonding process. However, ifwafers of 7740 Pyrex glass and silicon are used, for example, themajority of the deformation occurs in the lower melting point 7740 Pyrexglass.

Suitable materials for the substrate 302 and the membrane 304 may be7740 Pyrex glass and silicon, respectively; a suitable anodic bondingtemperature may be about 500° C.; and a suitable ratio of the inletcavity 308's maximum diameter to the inlet valve seat 310's height abovethe inlet cavity 308's bottom 328 may be at least about 100:1 andpreferably about 1000:1. The suitable anodic bonding temperature, andthe suitable ratio of the inlet cavity 308's maximum diameter to theinlet valve seat 310's height above the inlet cavity 308's bottom 328may vary, depending what materials are selected to form the substrate302 and the membrane 304.

Referring now to FIG. 32, the six square data points 324 are for themeasured flow rate (Q), in microliters per second, of the medication 12through the example one-way membrane valve 300, whose physicalparameters were set forth above; as a function of the driving pressuredifference (P), in nm Hg, across the one-way membrane valve 300. Themedication 12 was distilled water at about 23° C. The cross-hatched band326 shown in FIG. 32 is a plot of the predicted performance of theexample one-way membrane valve 300, whose physical parameters were setforth above, under a performance theory which will be discussed below. Atheoretical band 326 is plotted in FIG. 32, rather than a single line326, because the band 326 represents a height difference, between thetop surface 318 of the inlet valve seat 310 and the top surface 320 ofthe substrate 302, which ranges from about 2.0 microns to about 4.0microns.

When the above example one-way membrane valve 300, whose physicalparameters were set forth above, was tested in a reverse flow condition,the leak rate at 87.0 mm Hg was less than about 0.01 microliterssecond,which corresponds to a forward-to-reverse flow ratio in excess of 200:1.

It should be noted that, as seen in FIG. 30, because the inlet and theoutlet ports 306, 316 are located on opposite sides the one-way membranevalve 300, the valve 300 may be used either as a one-way inlet valve300, or as a one-way outlet valve 300, merely by turning it over.

It should also be noted that, if the valve 300 were mounted in itsintended location of use so that the top surface of the flexure 314 wasin close proximity to a flat surface, and so that at least some of themedication 12 exiting from the outlet port 316 had to pass through thegap between the flat surface and the top surface of the flexure 314,then the flexure 314 and the flat surface would, in effect, operate as aflow regulator similar to the radial flow regulator 32 of FIGS. 1-2, toregulate the flow of the medication 12 from the valve 300. In such acase, the flat surface would act as a regulator seat, similar to theregulator seat 42; the flexure 314 would act as a regulator flexure,similar to the regulator flexure 36; and the gap between the flexure 314and the flat surface would act as a regulator gap, similar to theregulator gap 48.

From the disclosures in this document, it is seen that it is possible toselectively design a one-way membrane valve 300 having any particulardesired forward flow rate (Q) of the medication 12 as a function of thedriving pressure difference (P) across the one-way membrane valve 300.This may be done by selectively adjusting one or more of the pertinentparameters, such as: (a) the stiffness, elasticity, resiliency, width,thickness, shape, and cross-sectional configuration of the flexure 314;(b) the amount the flexure 314 is prestressed, i.e., the heightdifference between the inlet valve seat 310's top surface 318 and thesubstrate 302's top surface 320; (c) the number size and shape of theinlet ports 306, the inlet cavity 308, and the outlet port 316; and (d)the driving pressure difference (P) across the one-way membrane valve300.

MICROMACHINED ONE-WAY MEMBRANE VALVE 300 HAVING A CIRCULAR FLEXURE AND ACIRCULAR INLET VALVE SEAT (FIGS. 30-32): MANUFACTURE

The micromachined one-way membrane valve 300 which is illustrated inFIGS. 30-31 is the same as, or at least similar to, the micromachinedone-way membrane valves 210, 240 of FIGS. 23-29 in its manufacture,except for those differences which will be made apparent by anexamination of all of the Figures and all of the disclosures in thisdocument.

Among those differences are that the desired height difference betweenthe top surfaces 318, 320 of the inlet valve seat 310 and the substrate302, respectively, may be obtained in any suitable way. One suitable waymay be, before the membrane 304 is manufactured and secured to thesubstrate 302, to etch all of the substrate 302's top surface 320(except for the inlet cavity 308 and the inlet valve seat 310), by anamount which is equal to the desired height difference. This etchingstep may be done in any suitable way, such as by using etching processeswhich is the same as, or at least similar to, that used to form theradial flow regulator 32's inlet channels 38, inlet cavity 40, regulatorseat 42 and outlet port 54 of FIGS. 1-2, except for those differences,if any, which will be made apparent by an examination of all of theFigures and disclosures in this document.

Alternatively, the desired height difference may be obtained bydepositing or securing, in any suitable way, a layer of any suitablematerial of the desired thickness on only the inlet valve seat 310's topsurface 318.

MICROMACHINED MEMBRANE FLOW SWITCH 250 (FIGS. 33-38): STRUCTURE

The micromachined membrane flow switch 250 of the present invention isillustrated in FIGS. 33-38. The flow switch 250 may comprise a substrate252 and a membrane 254.

The substrate 252 may have an inlet switch seat 256, an outlet cavity258 and a pair of outlet ports 260.

Although the substrate 252 is illustrated as being square, it may haveany other suitable size and shape.

Although the inlet switch seat 256 is illustrated as being cylindrical,and as having a flat top surface 270, it may have any other suitablesize and shape; and its top surface 270 may not be flat.

Although a single, cylindrical, ring-shaped outlet cavity 258 isillustrated, there could be more than one outlet cavity 258, and eachoutlet cavity 258 could have any other suitable size and shape.

Although a pair of outlet ports 260, each having a venturi-shapedgeometric configuration, for better fluid flow therethrough, areillustrated; there may be fewer or more outlet ports 260, and eachoutlet port 260 may have any other suitable size and shape.

The flow switch 250's membrane 254 may have a mounting portion 262,which may be secured to the substrate 252; a flexure 264, which extendsover the outlet cavity and part of the inlet switch seat 256; and aninlet port 266, which lies over the inlet switch seat 256.

Although the flexure 264 is illustrated as being ring shaped, and ashaving a uniform thickness, it may have any other suitable size andshape, and its thickness may not be uniform.

Although one, circular inlet port 266 is illustrated, there may be morethan one inlet port 266, and each inlet port 266 may have any othersuitable size and shape.

A switch gap 268 may be defined between the inlet switch seat 256 andthe flexure 264 when there is a zero driving pressure difference (P) ofthe medication 12 across the flow switch 250, which is the drivingpressure difference (P) between the flexure 264's top surface 265 andthe outlet ports 260.

By way of example, the flow switch 250 may have the following physicalparameters. The substrate 252 may be made from 7740 Pyrex glass, may bea square having sides about 5.0 mm long, and may have a maximumthickness of about 0.5 mm. The outlet cavity 258 may have an innerdiameter of about 2.0mm, an outer diameter of about 3.8 mm, and a depthof about 25 microns as measured from the substrate 252's top surface278. The outlet ports 260 may have a minimum diameter of about 100microns, and a length of about 475 microns. The inlet switch seat 256may have a diameter of about 2.0 mm, and a height above the outletcavity 258's bottom surface 280 of about 21 microns. The switch gap 268may be about 4 microns high, when there is a zero driving pressuredifference (P) of the medication 12 across the flow switch 250. Themembrane 254 may be made from epitaxial silicon, may have a thickness ofabout 25 microns, and may be a square having sides about 5.0 mm long.The flexure 264 may have an inner diameter of about 250 microns, and anouter diameter of about 3.8 mm. The inlet port 266 may have a diameterof about 250 microns.

The flow characteristics of this example flow switch 250 are illustratedin the graphs of FIGS. 35-38.

MICROMACHINED MEMBRANE FLOW SWITCH 250 (FIGS. 33-38): OPERATION ANDTHEORY

The flow switch 250 may be installed in its intended location of use inany suitable way. Any suitable medication supply means may be used toconnect the flexure 264's top surface 265 and the inlet port 266 to asource of the medication 12; and any suitable medication delivery meansmay be used to connect the flow switch 250's outlet ports 260 towhatever person, object or thing is to receive the medication 12 fromthe outlet ports 260.

For example, the flow switch 250 may be installed within any type ofreservoir means for the medication 12 by any suitable means, such as bylocating the flow switch 250's outlet ports 260 over the reservoirmeans's outlet, and by using an adhesive face seal between the flowswitch 250's bottom surface 282 and the inside of the reservoir means tohold the flow switch 250 in place. As a result, when the reservoir meansis filled with the medication 12, the flow switch 250 may be immersed inthe medication 12, with its inlet channel 266 and its flexure 264's topsurface 265 in fluid communication with the medication 12 within thereservoir means, and with its outlet ports 260 in fluid communicationwith the reservoir means' outlet. Such an installation for the flowswitch 250 may have numerous advantages.

For example, it is quick, easy, reliable and inexpensive, because noadditional medication supply means (such as supply conduits) are neededto supply the medication 12 to the inlet port 266 and the flexure 264'stop surface 265 (since they are already immersed in the medication 12);and because no additional medication delivery means (such as deliveryconduits) are needed to convey the medication 12 away from flow switch250's outlet ports 260, (since the reservoir means' outlet is used forthis purpose). Such additional inlet and outlet conduits may beundesirable since it may be relatively time consuming, difficult andexpensive to align and connect them to the flow switch 250, due to theextremely small size of the flexure 264, the inlet port 266, and theoutlet ports 260. Such additional inlet conduits may also be undesirablebecause they may tend to trap a bubble when being filled with a liquidmedication 12, which bubble might then be carried into the flow switch250 and cause it to malfunction.

When there is a zero driving pressure difference (P) of the medication12 across the flow switch 250, the flexure 264 is not bowed by themedication 12, and is essentially parallel to the inlet switch seat256's top surface 270.

However, during operation of the flow switch 250, as a driving pressuredifference (P) of the medication 12 is applied across the flow switch250, such as by pressurizing the source of the medication 12 withrespect to the flow switch 250's outlet port 260, by any suitable means,the medication 12 flows through the inlet port 266; flows radiallyoutwardly across the inlet valve seat 256's top surface 270 through theswitch gap 268; flows through the outlet cavity 258; and flows outthrough the outlet ports 260.

As the driving pressure difference (P) of the medication 12 across theflow switch 250 is increased from zero, the medication 12 graduallyforces the flexure 264 closer to the switch seat 268, thereby graduallydecreasing the height of the switch gap 268 (and vice versa).

Then, at a predetermined overpressure of the medication 12, i.e., at apredetermined driving pressure difference switch point (P_(SW)), theflexure 264 automatically begins an irreversible collapse that resultsin the flexure 264 being forced by the medication 12 against the inletswitch seat 256, and being held there by the medication 12, therebyautomatically closing the switch gap 268, switching off the flow switch250, and stopping the flow of the medication 12 through the flow switch250.

Then, when the driving pressure difference (P) across the flow switch250 is decreased to less than the predetermined overpressure, i.e., isdecreased to less than the predetermined driving pressure differenceswitch point (P_(SW)), the resiliency and elasticity of the flexure 264cause it to automatically move away from the inlet switch seat 256,thereby automatically opening the switch gap 268, switching the flowswitch 250 back on, and permitting the medication 12 to flow through theflow switch 250 once again.

As a result, it is seen that, at a predetermined overpressure of themedication 12, i.e., at a predetermined driving pressure differenceswitch point (P_(SW)), the flow switch 250 is automatically switchedoff, thereby stopping the flow of the medication 12 through the flowswitch 250; and that the flow switch 250 will not switch on again andpermit the medication 12 to flow through the flow switch 250 again untilthe overpressure condition is remedied i.e., until the driving pressuredifference (P) is decreased to less than the driving pressure differenceswitch point (P_(SW)).

The above operation of the flow switch 250 is illustrated in the graphof FIG. 35, whose flow curve 272 is for the example flow switch 250having the physical parameters that were set forth above. As seen inFIG. 35, the flow rate (Q) of the medication 12 through the flow switch250 increases as a function of the driving pressure difference (P)across the flow switch 250, up to the predetermined driving pressuredifference switch point (P_(SW)) of about 6.2 mm Hg. At thepredetermined driving pressure difference switch point (P_(SW)) of about6.2 mm Hg, the flow switch 250 automatically switches off, and the flowrate (Q) drops to zero as the flexure 264 is forced against the inletswitch seat 256, and held there, by the medication 12. When the flowswitch 250 has switched off, a high static pressure will occur acrossthe switch 250, since it is now the primary resistance to the flow ofthe medication 12.

Another way of interpreting the flow curve 272 is that as the flow rate(Q) of the medication 12 through the flow switch 250 increases, thedriving pressure difference (P) across the flow switch 250 increases asa function of the flow rate (Q), up to a predetermined flow rate switchpoint (Q_(SW)) of about 575 μLday. At the predetermined flow rate switchpoint (Q_(SW)) of about 575 μLday, the flow switch 250 automaticallyswitches off, and the flow rate (Q) drops to zero as the flexure 264 isforced against the inlet switch seat 256, and held there, by themedication 12.

The type of response curve 272 shown in FIG. 35 is highly desirable formany applications where, if the flow rate (Q) or the driving pressuredifference (P) of the medication 12 exceeds a predetermined nominallimit, such as due to an overpressure in the supply of the medication12, there may be undesirable consequences.

For example, if the outlet for a reservoir in a medication deliverydevice for the medication 12 was equipped with a flow switch 250, thenmedication delivery device may be designed for nominal operation below apredetermined flow rate switch point (Q_(SW)), or below a predetermineddriving pressure difference switch point (P_(SW)). Then, if either thepredetermined medication flow rate switch point (Q_(SW)) or thepredetermined driving pressure difference switch point (P_(SW)) isexceeded, such as if a medical person accidentally overfilled themedication delivery device's reservoir, the flow switch 250 would switchoff the flow of the medication 12 from the medication delivery deviceuntil the excessive driving pressure difference (P) was rectified. Thatwould significantly reduce the possibility of injury or death to thepatient due to an overdose of the medication 12 which might otherwiseoccur.

Referring now to the graphs of FIGS. 36-38, the thin plotted line 274 ineach graph is for the example flow switch 250, having the physicalparameters set forth above, except that its initial switch gap (at azero driving pressure difference (P) across the flow switch 250), is asindicated on the horizontal axis. The thick plotted line 276 in FIGS.36-38 is for the example flow switch 250, having the physical parametersset forth above, except that its inlet switch seat 256 has a diameter of0.5 mm, and its initial switch gap (at a zero driving pressuredifference (P) across the flow switch 250), is as indicated on thehorizontal axis.

In FIG. 36, the lines 274, 276 are the plots of the flow rate switchpoints (Q_(SW)) for the flow switches 250 as a function of the initialswitch gap 268 (at a zero driving pressure difference (P) across theflow switch 250). As seen in FIG. 36, the flow rate switch points(Q_(SW)) for the flow switches 250 are primarily set by the initialswitch gap 268; but that the diameter of the inlet switch seat 256 isalso significant, even though not as important.

FIG. 37 shows the driving pressure difference switch point (P_(SW)) forthe flow switches 250 as a function of the initial switch gap 268 (at azero driving pressure difference (P) across the flow switch 250). Asseen in FIG. 37, the driving pressure difference switch points (P_(SW))for the flow switches 250 are primarily set by the initial switch gap268; but that the diameter of the inlet switch seat 256 is alsosignificant, even though not as important.

FIG. 38 shows the switch point deflection of the flexure 264 at itsinlet port 266 (Dsw) for the flow switches 250 as a function of theinitial switch gap 268 (at a zero driving pressure difference (P) acrossthe flow switch 250). The switch point deflection (D_(SW)) is measuredas a fraction of the initial switch gap 268 (at a zero driving pressuredifference (P) across the flexure 264). As seen in FIG. 38, the switchpoint deflection (D_(SW)) is relatively constant over a range of valuesfor the initial switch gap 268.

The theory of operation of the flow switch 250, with its flow of themedication 12 through its switch gap 268 between its inlet switch seat256 and its flexure 264, is similar to the theory of operation set forthabove regarding the radial flow regulator 32 of FIGS. 1-2, and the flowof the medication 12 through its regulator gap 48 between its regulatorseat 42 and its flexure 28, except for those differences which will bemade apparent by an examination of all of the Figures and all of thedisclosures in this document.

For example, the curvature boundary conditions on the flexure 264 differfrom the curvature boundary conditions on the flexure 28, due to theflexure 264's inlet port 266.

In addition, the switch action of the flow switch 250's flexure 264 maybe attributable to the destabilization of the flexure 264 caused by atleast two things acting in concert. First, the destabilization of theflexure 264 may be caused by the fact that the outlet cavity 258 is atone of the lowest pressures in the flow switch 250. Since the flexure264's incremental face area over the outlet cavity 258 is a function ofthe square of the radius of the flexure 264, the flexure 264'sincremental face area is the greatest over the outlet cavity 258. Thus,there is a destabilizing leverage action exerted by the medication 12 onthe flexure 264 due to the driving pressure difference of the medication12 between the flexure's top surface 265 and the inside of the outletcavity 258. Second, the destabilization of the flexure 264 may also beassisted by the free rim of the flexure's inlet hole 266, which helps topermit the flexure 264 to change its position and snap against the inletswitch seat 256. On the other hand, in the radial flow regulator 32 themedication 12 is at a relatively higher pressure in the inlet channels38 and in the inlet cavity 40, as compared to the pressure of themedication in the regulator gap 48 and the outlet cavity 52, where theincremental face area of the flexure 28 is the least. So the regulator32's flexure 28 tends to not exhibit the snap action of the flow switch250's flexure 264.

From the disclosures in this document, it is possible to selectivelydesign a flow switch 250 having any particular desired characteristiccurve 272, 274, or 276; having any desired predetermined flow rateswitch point rate (Q_(SW)) for the medication 12; and having any desiredpredetermined driving pressure difference switch point (P_(SW)) for themedication 12. This may be done by selectively adjusting one or more ofthe pertinent parameters, such as: (a) the stiffness, elasticity,resiliency, thickness, size and shape of the flexure 264; (b) thenumber, size and shape of inlet port 266; (c) the size and shape of theinlet switch seat 256 and its top surface 270; (d) the size, shape andnumber of the outlet cavity 158 and the outlet ports 260; (e) the heightof the switch gap 268, when the driving pressure difference (P) acrossthe flow switch 250 is zero; and (f) the driving pressure difference (P)across the flow switch 250.

MICROMACHINED MEMBRANE FLOW SWITCH 250 (FIGS. 33-38): MANUFACTURE

The manufacture of the flow switch 250 is similar to the manufacture ofthe one-way valve 300 of FIGS. 30-31, except for those differences whichwill be made apparent by an examination of all of the Figures and all ofthe disclosures in this document.

For example, the desired initial switch gap 268 (at a zero drivingpressure difference (P) across the flexure 264), may be obtained byusing an etching process in which the inlet switch seat 256 is etched byan amount equal to the desired initial switch gap 268, while thesubstrate 252's top surface 278 is not etched at all.

MICROMACHINED RADIAL ARRAY FILTER 340 (FIGS. 39-40): STRUCTURE

The micromachined radial array filter 340 of the present invention isillustrated in FIGS. 39-40 as having been manufactured with a radialflow regulator 32 on the'same chip 342. The chip 342 may be disposable,in that it may discarded and replaced by a new chip 342 if the filter340 becomes clogged with filtered particles from the medication 12, orif the regulator 32 does not function properly.

Although the filter 340 and the regulator 32 are illustrated as having ageometric relationship in which the regulator 32 is nested inside of thefilter 340, for an unusually compact and space-saving configuration; thefilter 340 and the regulator 32 may have any other suitable geometricrelationship with respect to each other on the chip 342; and the filter340 and the regulator 32 may be located on separate chips. Although thefilter 340 is described as being used in conjunction with a regulator32, it may be used in conjunction with any other device, to supplyfiltered medication 12 to that device.

For clarity, the corresponding parts of the regulator 32 of FIGS. 39-40have been given the same reference numerals as the regulator 32 of FIGS.1-2, since the regulator 32 of FIGS. 39-40 has the same structure,operation, theory and manufacture as the regulator 32 of FIGS. 1-2,except for those differences which will be made apparent by anexamination of all of the Figures and all of the disclosures in thisdocument.

The filter 340 may comprise a substrate 34 and a membrane 36 which issecured to the substrate 34's top surface 46. The substrate 34 may havefour inlet ports 344; an inlet cavity 346; a radial array of twenty-twofilter slots 348, which alternate with twenty-two ribs 350; an outletcavity 352; and four outlet ports 354. The membrane 36 may form the topsurface of the inlet ports 344, the inlet cavity 346, the filter slots348, the outlet cavity 352, and the outlet ports 354.

Although four equally spaced inlet ports 344 are illustrated, eachhaving a rectangular cross-sectional configuration and following anarcuate path, there may be fewer or more inlet ports 344, the inletports 344 may not be equally spaced, each inlet port 344 may have anyother suitable size and shape, and each inlet port 344 may follow anyother suitable path, whether or not that path is straight. The functionsof each inlet port 344 may include transporting the medication 12 from asource of medication 12 to at least one inlet cavity 346.

Although only a single inlet cavity 346 is illustrated, having arectangular cross-sectional configuration, and following a ring-shapedpath, there may be more than one inlet cavity 346, each communicatingwith at least one inlet port 344 and at least one filter slot 348, eachinlet cavity 346 may have any other suitable size and shape, and eachinlet cavity 346 may follow any other suitable path, whether or not thatpath is straight. The functions of each inlet cavity 346 may includetransporting the medication 12 from at least one inlet port 344 to atleast one filter slot 348.

Although the inlet ports 344 and the inlet cavity 346 are illustrated asbeing discrete elements of the filter 340, they may be merged partiallyor wholly together, such as by enlarging the inlet ports 344 until theyperform some or all of the functions of the inlet cavity 346, or byenlarging the inlet cavity 346 until it performs some or all of thefunctions of the inlet ports 344.

Although a radial array of twenty-two identical filter slots 348 isillustrated, each filter slot 348 having a generally rectangularcross-sectional configuration, and a generally trapezoidal shape, thefilter slots 348 may be arranged in any other suitable way or array withrespect to each other, there may be fewer or more filter slots 348, eachfilter slot 348 may have any other suitable size, cross-sectionalconfiguration, and shape, and all of the filter slots 348 need not beidentical. The functions of the filter slots 348 may include removingundesired particles from the incoming medication 12; and guiding themedication 12 to the outlet cavity 352.

Although a radial array of twenty-two ribs 350 is illustrated, eachhaving a generally rectangular cross-sectional configuration and agenerally trapezoidal shape, the ribs 350 may be arranged in any othersuitable way or array with respect to each other, there may be fewer ormore ribs 350, and each rib 350 may have any other suitable size,cross-sectional configuration, and shape. The functions of the ribs 350may include helping to define the filter slots 348; and supporting themembrane 36.

Although a only a single outlet cavity 352 is illustrated, having asquare cross-sectional configuration, and following a ring-shaped path,there may be more than one outlet cavity 352, each communicating with atleast one filter slot 348 and at least one outlet port 354, each outletcavity 352 may have any other suitable size and shape, and each outletcavity 352 may follow any other suitable path, whether or not that pathis straight. The functions of each outlet cavity 352 may includetransporting the medication 12 from at least one filter slot 348 to atleast one outlet port 354.

Although four equally spaced outlet ports 354 are illustrated, eachhaving a rectangular cross-sectional configuration, and following astraight path, there may be fewer or more outlet ports 354, the outletports 354 may not be equally spaced, each outlet port 354 may have anyother suitable size and shape, and each outlet port 354 may follow anyother suitable path, whether or not that path is straight. The functionsof each outlet port 354 may include transporting the medication 12 awayfrom at least one outlet cavity 352, and delivering the medication 12 towhatever person, animal or thing may be receiving the medication 12 fromthe outlet port 354.

Although the outlet ports 354 and the outlet cavity 352 are illustratedas being discrete elements of the filter 340, they may be mergedpartially or wholly together, such as by enlarging the outlet ports 354until they perform some or all of the functions of the outlet cavity352, or by enlarging the outlet cavity 352 until it performs some or allof the functions of the outlet ports 354.

Although the outlet ports 354 are illustrated as forming the regulator32's inlet ports 38, the outlet ports 354 and the inlet ports 38 may bediscrete elements which may be fluidly connected in any suitable way byany suitable means.

By way of example, the filter 340 may have the following physicalparameters. The substrate 34 may be manufactured from 7740 Pyrex glass,may be a square having sides with a length of about 0.635 cm, and mayhave a maximum thickness of about 0.5 mm. Each inlet port 344 may have awidth of about 0.5 mm, a depth of about 10 microns, and a length ofabout 250 microns. The inlet cavity 346 may have a width of about 0.0127cm, a depth of about 10 microns, and an internal diameter of about 0.58cm. There may be 22 filter slots 348 and 22 ribs 350, and the sides ofeach filter slot 348 and each rib 350 may lay on a respective radial rayemanating from the center of the filter 340. Each filter slot 348 may beabout 0.10 to about 5.0 microns high. Each filter slot 348 and each rib350 may lie between an inner circle having a diameter of about 0.33 cm,and an outer circle having a diameter of about 0.58 cm. The outletcavity 352 may have a width of about 0.0254 cm, a depth of about 10microns, and an outer diameter of 0.33 cm. Each outlet port 354 may havea depth of about 10 microns, a width of about 250 microns, and a lengthof about 250 microns. The membrane 36 may be manufactured from siliconand may have a thickness of about 25 microns.

MICROMACHINED RADIAL ARRAY FILTER 340 (FIGS. 39-40): OPERATION ANDTHEORY

The chip 342, with its filter 340 and regulator 32, may be installed inits desired location of intended use in any suitable way. Any suitablemedication supply means may be used to connect the filter 340's inletports 344 to a source of the medication 12; and any suitable medicationdelivery means may be used to connect the regulator 32's outlet port 54to whatever person, animal or thing is to receive the medication 12 fromthe outlet port 54. The medication supply means may also be used tosupply the medication 12 to the flexure 28's top surface 62, at apressure which may or may not be the same as the pressure at which themedication 12 is supplied to the inlet ports 344.

For example, the chip 342 may be installed within any type of reservoirmeans for the medication 12 by any suitable means, such as by locatingthe regulator 32's outlet port 54 over the reservoir means's outlet, andby using an adhesive face seal between the substrate 34's bottom surface56 and the inside of the reservoir means to hold the chip 342 in place.As a result, when the reservoir means is filled with the medication 12,the chip 342 will be immersed in the medication 12, with the filter340's inlet ports 344 and the flexure 28's top surface 62 in fluidcommunication with the medication 12 within the reservoir means, andwith the regulator 32's outlet port 54 in fluid communication with thereservoir means' outlet. Such an installation for the chip 342 hasnumerous advantages.

For example, it is quick, easy, reliable and inexpensive, because noadditional medication supply means (such as supply conduits) are neededto supply the medication 12 to the filter 340's inlet ports 344 and tothe flexure 28's top surface 62 (since they are already immersed in themedication 12); and because no additional medication delivery means(such as delivery conduits) are needed to convey the medication 12 awayfrom the regulator 32's outlet port 54 (since the reservoir means'outlet is used for this purpose). Such additional inlet and outletconduits may be undesirable since it may be relatively time consuming,difficult and expensive to align and connect them to the chip 342, dueto the extremely small size of the filter 340's inlet ports 344, theflexure 28, and the regulator 32's outlet port 54. Such additional inletconduits may also be undesirable because they may tend to trap a bubblewhen being filled with a liquid medication 12, which bubble might thenbe carried into the filter 340 and the regulator 32 and cause them tomalfunction.

Alternatively, if the chip 342 did not have a regulator 32, but had onlya filter 340, then such a chip 342 may be installed in its intendedlocation of use in any suitable way. Any suitable medication supplymeans may be used to connect the filter 340's inlet ports 344 to asource of the medication 12; and any suitable medication delivery meansmay be used to connect the filter 340's outlet ports 354 to whateverperson, animal or thing is to receive the medication 12 from the outletports 354.

The driving pressure difference (P) across the filter 340 may be definedas the driving pressure difference (P) between the flexure 28's topsurface 62 and the outlet port 54. During operation, as a drivingpressure difference (P) is applied across the filter 340 in any suitableway, such as by pressurizing the source of medication 12 with respect tothe outlet port 54, the medication 12 will flow sequentially through thefilter 340's inlet ports 344, inlet cavity 346, filter slots 348, outletcavity 352, and outlet ports 354. From the filter 340's outlet ports354, the medication 12 will then flow sequentially through the regulator32 from its inlet ports 38 to its outlet port 54 in the manner which hasbeen described previously regarding the regulator 32 of FIGS. 1-2.

The size of the filter 340's filter slots 348 is selected to be suchthat the filter slots 348 will be able trap the smallest particle whichthe filter 340 is designed to remove from the medication 12. The size ofthe filter slots 348 may depend on the size of the smallest particlewhich can be tolerated by the person, animal or thing which is toreceive the filtered medication 12 from the filter 340. For example, ifthe filter 340 is intended to deliver the medication 12 to a regulator32, as illustrated in FIGS. 39-40, then preferably the filter 340'sfilter slots 348 may be chosen to have a size which is at least slightlysmaller than the size of the smallest fluid path dimension in theregulator 32, namely its regulator gap 48. In this way, the filter slots348 will be able to trap all of the particles in the medication 12 whichmight otherwise clog the smallest fluid path dimension in the regulator32.

It should be noted that the micromachining process for manufacturing thefilter slots 348 in the substrate 34 may easily manufacture filter slots348 which have a depth of from about 0.10 microns, or less, to about10.00 microns, or greater.

Any pressure exerted by the medication 12 on the membrane 36's topsurface 62 may be prevented from reducing the desired height orcross-sectional configuration of the inlet ports 344, the inlet cavity346, the filter slots 348, the outlet cavity 352 and the outlet ports354 in any suitable way, such as by selectively adjusting one or more ofthe pertinent parameters, such as: (a) the stiffness, elasticity,resiliency, thickness, size, shape and cross-sectional configuration ofthe membrane 36; and (b) the length, width, size and shape of the inletports 344, the inlet cavity 346, the filter slots 348, the outlet cavity352 and the outlet ports 354.

For the longest, most effective life of the filter 340, it may bepreferred that all of the filter slots 348 be utilized an approximatelyequal amount. This goal may be at least partially achieved in anysuitable way, such as by selectively adjusting one or more of thepertinent parameters, such as: (a) selecting the cross-sectional area ofthe filter 340's inlet cavity 346 to be large enough so that thepressure drop of the medication 12 in the inlet cavity 346 between theadjacent inlet ports 344 may be reduced, or minimized, to the point thatthe flow of the medication 12 from the inlet ports 344 is distributed atleast approximately equally by the inlet cavity 346 to each of thefilter slots 348; (b) selecting the cross-sectional area of the filter340's outlet cavity 352 to be large enough so that the pressure drop ofthe medication 12 in the outlet cavity 346 between adjacent outlet ports354 may be reduced, or minimized, to the point that the outgoing flow ofmedication 12 is distributed at least approximately equally by theoutlet cavity 352 to each of the outlet ports 354; and (c) selecting thecross-sectional areas of the filter 340's inlet cavity 346 and outletcavity 352 so that the pressure drop of the medication 12 across each ofthe filter slots 348 may be at least approximately equal.

The fluid resistance of the filter 340 to the medication 12 may beselectively adjusted in any suitable way, such as by selectivelyadjusting at least one of the pertinent parameters, such as the number,length, size, shape and path followed by the inlet ports 344, the inletcavity 246, the outlet cavity 352, the outlet ports 354, and the filterslots 348.

The filter 340 may be designed to have a small, or negligible, fluidflow resistance to the medication 12 when new, in order to provide amargin for an accumulation of filtered particles in the filter slots348. That is, the filter 340 may be designed so that after apredetermined quantity of particles have been trapped by the filterslots 348, a predetermined minimum fluid flow rate (Q) of the medication12, at a predetermined driving pressure difference (P) across the filter340, will still be permitted to flow through the filter 340. If this isdone, and if the filter 340 is used in conjunction with a regulator 32,such as is seen in FIGS. 39-40, then any fluid flow resistance of themedication 12 within the regulator 32 which is needed for properpressure bias of the flexure 28 may be provided by the regulator 32 'sinlet ports 38 and inlet cavity 40.

Alternatively, the fluid flow resistance of the filter 340 may beselected to have a significant fluid flow resistance to the medication12 when new, in order to provide for proper pressure bias of theregulator 32's flexure 28. In other words, such a filter 340 may providethe dual functions of: (a) filtering out undesired particles from themedication 12; and (b) defining the flow rate operating point of theregulator 32, i.e., defining the maximum flow rate (Q) of the medication12 through the regulator 32. In this case, the flow rate (Q) of themedication 12 through the filter 340 may fall as its filter slots 348become clogged with filtered particles during use, and it may be prudentto provide some level of medication pre-filtering.

In general, it may be advantageous to provide the filter 340 withmedication 12 which has been pre-filtered to a substantial degree toremove undesired particles from the medication 12 which are larger thanthe smallest particles which the filter 340 is intended to trap. By suchpre-filtering of large particles from the medication 12, the useful lifeof the filter 340 may be greatly extended, since the filter 340 is aprecision filter for filtering very small particles, and thus it maytake only a relatively small number of large particles to clog it.

MICROMACHINED RADIAL ARRAY FILTER 340 (FIGS. 39-40): MANUFACTURE

The substrate 34 may be manufactured from any suitable strong, durablematerial which is compatible with the medication 12; in which the filter340's inlet ports 344, inlet cavity 346, filter slots 358, outlet cavity352 and outlet ports 354 may be manufactured in any suitable way; and inwhich the regulator 32's inlet channels 38, inlet cavity 40, regulatorseat 42, outlet cavity 52, and outlet port 54 may be manufactured in anysuitable way. Suitable ways may include using any suitable etching,molding, stamping and machining process. Such a machining process mayinclude the use of physical tools, such as a drill; the use ofelectromagnetic energy, such as a laser; and the use of a water jet.

The membrane 36 may be manufactured from any suitable strong, durable,flexible, material which is compatible with the medication 12.

If the filter 340 and the regulator 32 are intended to regulate amedication 12 which is to be supplied to a human or an animal, then anypart of the filter 340 and the regulator 32 which is exposed to themedication 12 should be manufactured from, and assembled or bonded with,non-toxic materials. Alternatively, any toxic material which is used tomanufacture the filter 340 and the regulator 32, and which is exposed tothe medication 12 during use of the filter 340 and the regulator 32, maybe provided with any suitable non-toxic coating which is compatible withthe medication 12.

Suitable materials for the substrate 34 and the membrane 36 may bemetals (such as titanium), glasses, ceramics, plastics, polymers (suchas polyimides), elements (such as silicon), various chemical compounds(such as sapphire, and mica), and various composite materials.

The substrate 34 and the membrane 36 may be assembled together in anysuitable leak-proof way. Alternatively, the substrate 34 and themembrane 36 may be bonded together in any suitable leak-proof way, suchas by anodically bonding them together; such as by fusing them together(as by the use of heat or ultrasonic welding); and such as by using anysuitable bonding materials, such as adhesive, glue, epoxy, solvents,glass solder, and metal solder.

Anodically bonding the substrate 34 and the membrane 36 together may bepreferable for at least four reasons; which reasons were discussedpreviously regarding the regulator 32 of FIGS. 1-2.

One example of how the chip 342, with its filter 340 and regulator 32,may be manufactured will now be given. The starting point may be a 76.2mm diameter wafer of Corning 7740 Pyrex glass, which will form thesubstrate 34.

The filter 340's inlet ports 344, inlet cavity 346, filter slots 348,outlet cavity 352, and outlet ports 354; and the FIGS. 39-40 regulator32's inlet channels 38, inlet cavity 40, regulator seat 42 and outletcavity 52 may be manufactured in the substrate 34 in any suitable way.One suitable way may be to use an etching process which is the same as,or at least similar to, that used to manufacture the FIGS. 1-2 regulator32's inlet channels 38, inlet cavity 40, regulator seat 42 and outletcavity 52, except for those differences, if any, which will be madeapparent by an examination of all of the Figures and disclosures in thisdocument.

The FIGS. 39-40 outlet port 54 may then be manufactured in the substrate34 in any suitable way. One suitable way may be use a laser drillingprocess which is the same as, or at least similar to, that used tomanufacture the FIGS. 1-2 regulator 32's outlet port 54, except forthose differences, if any, which will be made apparent by an examinationof all of the Figures and disclosures in this document.

A layer of corrosion-resistant material(s) may then be applied to all ofthe surfaces of the filter 340's inlet ports 344, inlet cavity 346,filter slots 348, outlet cavity 352 and outlet ports 354; and to all ofthe surfaces of the FIGS. 39-40 regulator 32's inlet channels 38, inletcavity 40, regulator seat 42, outlet cavity 52, and outlet port 54 inany suitable way. One suitable way may be to use an application processwhich is the same as, or at least similar to, that used to apply a layerof corrosion-resistant material(s) to the FIGS. 1-2 regulator 32's inletchannels 38, inlet cavity 40, regulator seat 42, outlet cavity 52, andoutlet port 54, except for those differences, if any, which will be madeapparent by an examination of all of the Figures and disclosures in thisdocument.

The FIGS. 39-40 membrane 36 may be manufactured from a silicon wafer,and secured to the glass wafer (which is the FIGS. 39-40 substrate 34),in any suitable way. One suitable way may be to use a manufacturing andsecuring process which is the same as, or at least similar to, that usedto manufacture the FIGS. 1-2 membrane 36, and to secure it to the FIGS.1-2 substrate 34, except for those differences, if any, which will bemade apparent by an examination of all of the Figures and disclosures inthis document.

As was mentioned above, although the filter 340 is illustrated in FIGS.39-40 as being manufactured on the chip 342 with a regulator 32, thefilter 340 may be manufactured by itself on the chip 342, without aregulator 32.

In such a case, all or part of the filter 340's outlet ports 354 mayextend from the outlet cavity 352 down through the substrate 34 (in afashion similar to the regulator 32's outlet port 54). Such downwardlyextending outlet ports 354 for the filter 340 may have any suitableshape, such as a venturi shape; and may be manufactured in any suitableway. One suitable way may be use a laser drilling process which is thesame as, or at least similar to, that used to manufacture the FIGS. 1-2regulator 32's outlet port 54, except for those differences, if any,which will be made apparent by an examination of all of the Figures anddisclosures in this document.

The manufacture of only one filter 340, and the manufacture of only onefilter 340regulator 32 combination were described above. However, itwill be appreciated that on any pair of glass and silicon wafers thesubstrates 34 and the membranes 36 for a large number of filters 340, orfilter 340regulator 32 combinations could be manufactured simultaneouslyin a manner similar to that described above. If such is the case, anarray of substrates 34 may be simultaneously etched in the glass wafer;their outlet ports 54 may be drilled, and the layer of one or morecorrosion-resistant substances may be applied to the substrates 34. Thenthe silicon and glass wafers for the substrates 34 and the membranes 36may be aligned and secured together. Then, all of the membranes 36 maybe manufactured simultaneously by grinding and etching the silicon waferto its desired final thickness. The siliconglass substrate 34membrane 36sandwich may then be divided by any suitable means (such as dicing) intoindividual chips, each chip bearing at least one filter 340 or filter340regulator 32 combination.

One of the advantages of using etching and anodic bonding processes tomanufacture the filter 340, and the filter 340regulator 32 combination,is that such processes enable high quality, very reliable filters 340,and filter 340regulator 32 combinations, to be mass produced in greatnumbers at a cost so low that the filters 340 and the filter340regulator 32 combinations may be considered to be disposable.

Further, it should also be noted that the filter 340 and the filter340regulator 32 combination are stunning in their simplicity since theyboth have only two basic parts, i.e. their substrates 34 and theirmembranes 36; and since the regulator 32 has only one moving part, i.e.,its flexure 28, which merely bows during operation of the filter340regulator 32 combination. In addition, because the raw materials fromwhich the filter 340 and the filter 340regulator 32 combination may bemanufactured may be very inexpensive, such as glass and silicon, thecost of the filter 340 and the filter 340regulator 32 combination mayheld to a very low level.

MICROMACHINED SLAB FILTER 380 (FIGS. 41-43): STRUCTURE

The micromachined slab filter 380 of the present invention isillustrated in FIGS. 41-43 as having been manufactured with a radialflow regulator 32 on the same chip 342. The chip 342 may be disposable,in that it may discarded and replaced by a new chip 342 if the filter380 becomes clogged with filtered particles from the medication 12, orif the regulator 32 does not function properly.

Although the filter 380 and the regulator 32 are illustrated as having ageometric relationship in which the filter 380 is along side of theregulator 32, the filter 380 and the regulator 32 may have any othersuitable geometric relationship with respect to each other on the chip342. For example, the filter 380 may be ring-shaped and sized so thatthe regulator 32 may be nested inside of the ring-shaped filter 380(similar to the arrangement of the radial array filter 340 and theregulator 32 of FIGS. 39-40).

Although the filer 380 and the regulator 32 are illustrated as being onthe same chip 342, the filter 380 and the regulator 32 may be located onseparate chips.

Although the filter 380 is described as being used in conjunction with aregulator 32, it may be used in conjunction with any other device, tosupply filtered medication 12 to that device.

For clarity, the corresponding parts of the regulator 32 of FIGS. 41-43have been given the same reference numerals as the regulator 32 of FIGS.1-2, since the regulator 32 of FIGS. 41-43 has the same structure,operation, theory and manufacture as the regulator 32 of FIGS. 1-2,except for those differences which will be made apparent by anexamination of all of the Figures and all of the disclosures in thisdocument.

The filter 380 may comprise a substrate 34; a filter element 390; and amembrane 36, which is secured to the substrate 34's top surface 46.

The membrane 36 may have an inlet port 388.

The substrate 34 may have a recessed filter mounting lip 382, forreceiving the filter element 390's edges; an outlet cavity 384, which isat least partially surrounded by the recessed filter mounting lip 382;and a pair of outlet ports 386.

Although only one, rectangular inlet port 388, filter mounting lip 382,filter element 390, and outlet cavity 384 are illustrated, there may bemore than one of any of these elements, and any of these elements mayhave any other suitable size and shape. And although only two, straightoutlet ports 386 are illustrated, each having a rectangularcross-sectional configuration, there may be fewer or more outlet ports386, each outlet port 386 may have any other suitable size and shape,and each outlet port 386 may follow any suitable path, whether or notthat path is straight. For example, there may be an array of filtermounting lips 383, filter elements 390, and outlet cavities 384; eachcommunicating, directly or indirectly, with at least one inlet port 388and at least one outlet port 386.

The filter element 390's edges may be held in place by being sandwichedbetween the filter mounting lip 382 and the membrane 36. In such a case,the depth of the filter mounting lip 382 may be selected to be about thesame as the thickness of the filter element 390's edges.

An adhesive 394, which is compatible with the medication 12, may be usedto help hold the filter element 390's edges in place between the filtermounting lip 382 and the membrane 36; and to provide a seal between thefilter mounting lip 382, the filter element 390's edges, and themembrane 36. In such a case, the depth of the filter mounting lip 382may be selected to be greater than the thickness of the filter element390's edges, in order to provide room for the adhesive 394.

The seal between the filter mounting lip 382, the filter element 390'sedges, and the membrane 36 may help to prevent any leakage of theunfiltered medication 12 around the filter element 390's edges, and intothe outlet cavity 384. However, such a seal may not be needed if thetolerances of the filter 380 are such that the largest gap between thefilter mounting lip 382, the filter element 390's edges, and themembrane 36 is smaller than the smallest particle in the medication 12which the filter 380 is designed to filter out of the medication 12.

Alternatively, the filter mounting lip 382 may be eliminated and thefilter element 390's edges may be mounted either on top of, or under,the membrane 36 by any suitable means, such as by using any suitableadhesive or bonding process.

The outlet cavity 384 may be provided with at least one filter elementsupport (not illustrated, for clarity). The functions of each filterelement support may include helping to prevent those portions of thefilter element 390 which lie over the outlet cavity 384 from collapsingdown into the out let cavity 384, while simultaneously not undulyinterfering with the flow of the medication 12 through the outlet cavity384 to the outlet ports 86. Each filter element support may have anysuitable size and shape, such as like the pump 130's radial spine typemembrane supports 148 (see FIGS. 16-17), or the pump 180's cylindricalpin type membrane supports 148 (see FIGS. 18-19).

By way of example, the filter 380 may have the following physicalparameters. The substrate 34 may be manufactured from 7740 Pyrex glass,may be a square having sides with a length of about 0.635 cm, and mayhave a maximum thickness of about 1.0 mm. The filter mounting lip 382may have a length of about 4.6 mm; a width of about 1.8 mm; and a depthof about 65 microns, as measured from the substrate 34's top surface 46.The outlet cavity may have a length of about 4.0 mm; a width of about1.5 mm; and a depth of about 25 microns, as measured from the substrate34's top surface 46. The outlet ports 386 may have a length of about 3.0mm; a width of about 250 microns; and a depth of about 25 microns, asmeasured from the substrate 34's top surface 46. The filter element 390may be made from Anopore inorganic membrane having a maximum pore sizeof about 0.1 microns, (the Anopore inorganic membrane is described inmore detail below). The filter element 390 may have a filter area about1.5 mm wide and about 4.0 mm long. The membrane 36 may be made fromsilicon, and may have a thickness of about 25 microns.

When the medication 12 is distilled water, the example filter 380,having the physical parameters set forth, may have a flow rate of about1.0 ccday, with a pressure drop across the filter element 290 of about5.15 mm Hg.

MICROMACHINED SLAB FILTER 380 (FIGS. 41-43): OPERATION AND THEORY

The chip 342, with its filter 380 and regulator 32, may be installed inits desired location of intended use in any suitable way. Any suitablemedication supply means may be used to connect the filter 380's inletport 388 to a source of the medication 12; and any suitable medicationdelivery means may be used to connect the regulator 32's outlet port 54to whatever person, animal or thing is to receive the medication 12 fromthe outlet port 54. The medication supply means may also be used tosupply the medication 12 to the flexure 28's top surface 62, at apressure which may or may not be the same as the pressure at which themedication 12 is supplied to the inlet port 388.

For example, the chip 342 may be installed within any type of reservoirmeans for the medication 12 by any suitable means, such as by locatingthe regulator 32's outlet port 54 over the reservoir means's outlet, andby using an adhesive face seal between the substrate 34's bottom surface56 and the inside of the reservoir means to hold the chip 342 in place.As a result, when the reservoir means is filled with the medication 12,the chip 342 will be immersed in the medication 12, with the filter380's inlet port 388 and the flexure 28's top surface 62 in fluidcommunication with the medication 12 within the reservoir means, andwith the regulator 32's outlet port 54 in fluid communication with thereservoir means' outlet. Such an installation for the chip 342 hasnumerous advantages.

For example, it is quick, easy, reliable and inexpensive, because noadditional medication supply means (such as supply conduits) are neededto supply the medication 12 to the filter 380's inlet port 388 and tothe flexure 28's top surface 62 (since they are already immersed in themedication 12); and because no additional medication delivery means(such as delivery conduits) are needed to convey the medication 12 awayfrom the regulator 32's outlet port 54 (since the reservoir means'outlet is used for this purpose). Such additional inlet and outletconduits may be undesirable since it may be relatively time consuming,difficult and expensive to align and connect them to the chip 342, dueto the extremely small size of the filter 380's inlet port 388, theflexure 28, and the regulator 32's outlet port 54. Such additional inletconduits may also be undesirable because they may tend to trap a bubblewhen being filled with a liquid medication 12, which bubble might thenbe carried into the filter 380 and the regulator 32 and cause them tomalfunction.

Alternatively, if the chip 342 did not have a regulator 32, but had onlya filter 380, then such a chip 342 may be installed in its intendedlocation of use in any suitable way. Any suitable medication supplymeans may be used to connect the filter 380's inlet port 388 to a sourceof the medication 12; and any suitable medication delivery means may beused to connect the filter 380's outlet ports 386 to whatever person,animal or thing is to receive the medication 12 from the outlet ports386.

The driving pressure difference (P) across the filter 380 may be definedas the driving pressure difference (P) between the flexure 28's topsurface 62 and the outlet port 54. During operation, as a drivingpressure difference (P) is applied across the filter 380 in any suitableway, such as by pressurizing the source of medication 12 with respect tothe outlet port 54, the medication 12 will flow sequentially through thefilter 380's inlet port 388, filter element 390, outlet cavity 384, andoutlet ports 386. From the filter 380's outlet ports 386, the medicationwill then flow sequentially through the radial flow regulator 32 fromits inlet ports 38 to its outlet port 54 in the manner which has beendescribed previously regarding the radial flow regulator 32 of FIGS.1-2.

The pore size of the filter element 390 is selected to be such that thefilter element 390 will be able trap the smallest particle which thefilter 380 is designed to remove from the medication 12. The pore sizeof the filter element 390 may depend on the size of the smallestparticle which can be tolerated by the person, animal or thing which isto receive the filtered medication 12 from the filter 380. For example,if the filter 380 is intended to deliver the medication 12 to aregulator 32, as illustrated in FIGS. 41 43, then preferably the poresize of the filter element 390 may be chosen to have a size which is atleast slightly smaller than the size of the smallest fluid pathdimension in the regulator 32, namely its regulator gap 48. In this way,the filter element 390 will be able to trap all of the particles in themedication 12 which might otherwise clog the smallest fluid pathdimension in the regulator 32.

The flow rate (Q) of the medication 12 through the filter element 390may selected in any suitable way, such as by selectively adjusting oneor more of the pertinent parameters, such as: (a) the driving pressuredifference (P) across the filter 390; (b) the filter area of the filterelement 390, that is the portion of the filter element 390 which isexposed to the medication 12 during use; and (c) the filter element390's pore size.

The useful life of the filter 380 is over when so many of the filterelement 390's pores have been clogged by particles filtered from themedication 12 that, at the maximum desired driving pressure difference(P) across the filter 380, the minimum desired flow rate (Q) of themedication 12 through the filter 380 can no longer be achieved. Thus,both the flow rate (Q) and the useful life of the filter 380 is afunction of how many of the filter element 390's pores have been cloggedby particles filtered from the medication 12. For any given pore size ofthe filter element 390, the useful life of the filter 380 may beselectively increased or decreased, respectively, by selectivelyincreasing or decreasing the filter area of the filter element 390.

In general, it may be advantageous to provide the filter 380 withmedication 12 which has been pre-filtered to a substantial degree toremove undesired particles from the medication 12 which are larger thanthe smallest particles which the filter 380 is intended to trap. By suchpre-filtering of large particles from the medication 12, the useful lifeof the filter 380 may be greatly extended, since the filter 380 is aprecision filter for filtering very small particles, and thus it maytake only a relatively small number of large particles to clog it.

The driving pressure difference (P) across the filter 380 may tend tocause portions of the filter element 390 to bow towards the outletcavity 384's bottom surface 385. A problem may arise if any portions ofthe filter element 390 are forced against the cavity 384's bottom 385,since those portions of the filter element 390 would no longer be ableto perform their intended filtering function. This problem may beaddressed in any suitable way, such as by selectively adjusting one ormore of the pertinent parameters, such as (a) the number, size, shapeand location of any filter element supports for the filter element 390which may be provided in the outlet cavity 384; (b) the size, shape anddepth of the outlet cavity 384; and (c) the stiffness, elasticity,resiliency, thickness, cross-sectional configuration, size and shape ofthe filter element 390.

The fluid resistance of the filter 380 to the medication 12 may beselectively adjusted in any suitable way, such as by selectivelyadjusting at least one of the pertinent parameters, such as: (a) thenumber, size, and shape of the inlet port 388; (b) the number, size,shape, thickness and pore size of the filter element 390; (c) thenumber, size, shape, and depth of the outlet cavity 384; (d) the number,size, shape and location of any filter element supports in the outletcavity 384 for the filter element 390; and (e) the number, length, size,shape, and path followed by each of the outlet ports 386.

The filter 380 may be designed to have a small, or negligible, fluidflow resistance to the medication 12 when new, in order to provide amargin for an accumulation of filtered particles in the filter element390's pores. That is, the filter 380 may be designed so that after apredetermined quantity of particles have been trapped in the filterelement 390's pores, a predetermined minimum fluid flow rate (Q) of themedication 12, at a predetermined driving pressure difference (P) acrossthe filter 380, will still be permitted to flow through the filter 380.If this is done, and if the filter 380 is used in conjunction with aradial flow regulator 32, such as is seen in FIGS. 41-43, then any fluidflow resistance of the medication 12 within the radial flow regulator 32which is needed for proper pressure bias of the regulator portion 58 ofthe regulator 32's membrane 36, may be provided by the regulator 32'sinlet ports 38 or inlet cavity 40.

Alternatively, the fluid flow resistance of the filter 380 may beselected to have a significant fluid flow resistance to the medication12 when new, in order to provide for proper pressure bias of theregulator portion 58 of the regulator 32's membrane 36. In other words,such a filter 380 may provide the dual functions of: (a) filtering outundesired particles from the medication 12; and (b) defining the flowrate operating point of the radial flow regulator 32, that is, definingthe maximum flow rate (Q) of the medication 12 through the radial flowregulator 32. In this case, the flow of the medication 12 through thefilter 380 may fall as the filter element 390's pores become cloggedwith filtered particles during use, and it may be prudent to providesome level of the pre-filtering for the medication 12 which wasdiscussed above.

MICROMACHINED SLAB FILTER 380 (FIGS. 41-43): MANUFACTURE

The substrate 34 may be manufactured from any suitable strong, durablematerial which is compatible with the medication 12; in which the filter380's mounting lip 382, outlet cavity 384, filter element supports (ifany), and outlet ports 386 may be manufactured in any suitable way; andin which the regulator 32's inlet channels 38, inlet cavity 40,regulator seat 42, outlet cavity 52, and outlet port 54 may bemanufactured in any suitable way. Suitable ways may include using anysuitable etching, molding, stamping and machining process. Such amachining process may include the use of physical tools, such as adrill; the use of electromagnetic energy, such as a laser; and the useof a water jet.

The membrane 36 may be manufactured from any suitable strong, durable,flexible, material which is compatible with the medication 12, and inwhich the inlet port 388 may be manufactured in any suitable way, suchas by using any suitable etching, molding, stamping and machiningprocess. Such a machining process may include the use of physical tools,such as a drill or saw; the use of electromagnetic energy, such as alaser; and the use of a water jet.

The filter element 390 may be manufactured from any suitable strong,durable material which is compatible with the medication 12, which willpermit the desired flow rate (Q) of the medication 12, which canwithstand the desired driving pressure (P) across the filter 380, whichhas a pore size smaller than the smallest particle which is desired tobe filtered from the medication 12, and which will not generateparticles which may contaminate the medication 12. The filter element390 may be designed to filter out any particular size of particle fromthe medication 12, depending on the intended use of the filter 380.

If the filter 380 and the regulator 32 are intended to regulate amedication 12 which is to be supplied to a human or an animal, then anypart of the filter 380 and the regulator 32 which is exposed to themedication 12 should be manufactured from, and assembled or bonded with,non-toxic materials. Alternatively, any toxic material which is used tomanufacture the filter 380 and the regulator 32, and which is exposed tothe medication 12 during use of the filter 380 and the regulator 32, maybe provided with any suitable non-toxic coating which is compatible withthe medication 12.

Suitable materials for the substrate 34 and the membrane 36 may bemetals (such as titanium), glasses, ceramics, plastics, polymers (suchas polyimides), elements (such as silicon), various chemical compounds(such as sapphire, and mica), and various composite materials.

Suitable materials for the filter element 390 may be any suitableorganic material having suitably sized pores in it, such as a thinpolymer which has pores generated in it by using nuclear particlebombardment. Such a filter element 390 may be Nuclepore material made bythe Nuclepore Corporation of Pleasanton, Calif., which may have amaximum pore size selected to be in the 0.03 to 12.0 micron range.

Alternatively, the filter element 390 may be manufactured from anysuitable inorganic material, such as glass, ceramic or metal which hassuitably sized pores in it. For example, the filter element 390 may bemade from electrolytically etched aluminum. Such a filter element 390may be Anopore inorganic membrane, made by Whatman, Inc. of Clifton,N.J., which may have a maximum pore size selected to be in the 0.02 to0.2 micron range.

Alternatively The filter 380's membrane 36 may be manufactured from thesame materials which were used to manufacture the membrane 36.

The substrate 34, the membrane 36 and the filter element 390 may beassembled together in any suitable leak-proof way. Alternatively, thesubstrate 34, the membrane 36, and the filter element 390 may be bondedtogether in any suitable leak-proof way, such as by anodically bondingthem together; such as by fusing them together (as by the use of heat orultrasonic welding); and such as by using any suitable bondingmaterials, such as adhesive, glue, epoxy, solvents, glass solder, andmetal solder. The substrate 34 and the membrane 36 may not necessarilybe assembled or bonded together with each other in the same way in whichthe substrate 34, the membrane 36 and the filter element 390 areassembled or bonded together with each other.

Anodically bonding the substrate 34, the membrane 36 and the filterelement 390 together may be preferable for at least four reasons; whichreasons are the same as, or at least similar to the reasons discussedpreviously regarding anodically bonding together the substrate 34 andthe membrane 36 of the regulator 32 of FIGS. 1-2.

One example of how the chip 342, with its filter 380 and regulator 32,may be manufactured will now be given. The starting point may be a 76.2mm diameter wafer of Corning 7740 Pyrex glass, which will form thesubstrate 34.

The filter 380's mounting lip 382, outlet cavity 384, filter elementsupports (if any), and outlet ports 386; and the FIGS. 41-43 regulator32's inlet channels 38, inlet cavity 40, regulator seat 42 and outletcavity 52 may be manufactured in the substrate 34 in any suitable way.One suitable way may be to use an etching process which is the same as,or at least similar to, that used to manufacture the FIGS. 1-2 regulator32's inlet channels 38, inlet cavity 40, regulator seat 42 and outletcavity 52, except for those differences, if any, which will be madeapparent by an examination of all of the Figures and disclosures in thisdocument.

The FIGS. 41-43 outlet port 54 may then be manufactured in the substrate34 in any suitable way. One suitable way may be use a laser drillingprocess which is the same as, or at least similar to, that used tomanufacture the FIGS. 1-2 regulator 32's outlet port 54, except forthose differences, if any, which will be made apparent by an examinationof all of the Figures and disclosures in this document.

A layer of corrosion-resistant material(s) may then be applied to all ofthe surfaces of the filter 340's mounting lip 382, outlet cavity 384,filter element supports (if any), and outlet ports 386; and to all ofthe surfaces of the FIGS. 41-43 regulator 32's inlet channels 38, inletcavity 40, regulator seat 42, outlet cavity 52, and outlet port 54 inany suitable way. One suitable way may be to use an application processwhich is the same as, or at least similar to, that used to apply a layerof corrosion-resistant material(s) to the FIGS. 1-2 regulator 32's inletchannels 38, inlet cavity 40, regulator seat 42, outlet cavity 52, andoutlet port 54, except for those differences, if any, which will be madeapparent by an examination of all of the Figures and disclosures in thisdocument.

The filter element 390 then be placed 6n the substrate 34 with its edgesbeing supported by the filter mounting lip 382 and with its centralportions being supported by the filter element supports (if any).

The membrane 36, with its inlet port 388, may be manufactured from asilicon wafer, and secured to the glass wafer (which is the substrate34) in any suitable way. The structure, operation, theory andmanufacture of the filter 380's membrane 36, with its inlet port 388,the securing of the membrane 36 to its substrate 34 is the same as, orat least similar to, the manufacturing of the linear flow regulator 80'smembrane 84, with its inlet port 88, and the securing of its membrane 84to its substrate 86, except for those differences, if any, which will bemade apparent by an examination of all of the Figures and disclosures inthis document.

It may be preferred that the filter element 390 be made from aninorganic membrane, such as the etched aluminum membrane which wasdescribed above, if the filter 380's substrate 34 and membrane 36 arebonded together by using a high temperature process, such as the anodicbonding process which was described above regarding the FIGS. 1-2regulator 32's substrate 34 and membrane 36. That would offer severaladvantages, such as allowing the filter element 390 to be simultaneouslyincorporated into the filter 380 during the manufacture of the regulator32 on the chip 342; allowing the edges of the filter element 590 to besimultaneously anodically bonded to the substrate 34 and membrane 36(thereby eliminating the need for any other bonding and sealingmaterials for this purpose); and permitting the high anodic bondingtemperature, to simultaneously burn out or volatilize any organic debriswhich may be located within the filter 380 and regulator 32.

As was mentioned above, although the filter 380 is illustrated in FIGS.41-43 as being manufactured on the chip 342 with a regulator 32, thefilter may be manufactured by itself on the chip 342, without aregulator 32.

In such a case, all or part of the filter 380's outlet ports 386 mayextend from the outlet cavity 384 down through the substrate 34 (in afashion similar to the regulator 32's outlet port 54). Such downwardlyextending outlet ports 386 for the filter 380 may have any suitableshape, such as a venturi shape; and may be manufactured in any suitableway. One suitable way may be use a laser drilling process which is thesame as, or at least similar to, that used to manufacture the FIGS. 1-2regulator 32's outlet port 54, except for those differences, if any,which will be made apparent by an examination of all of the Figures anddisclosures in this document.

The manufacture of only one filter 380, and the manufacture of only onefilter 380regulator 32 combination were described above. However, itwill be appreciated that on any pair of glass and silicon wafers thesubstrates 34 and the membranes 36 for a large number of filters 380, orfilter 380regulator 32 combinations could be manufactured simultaneouslyin a manner similar to that described above. If such is the case, anarray of substrates 34 may be simultaneously etched in the glass wafer;their outlet ports 54 may be drilled, and the layer of one or morecorrosion-resistant substances may be applied to the substrates 34. Thenan array of inlet ports 288 may be simultaneously etched in the siliconwafer. Then the silicon and glass wafers for the substrates 34 and themembranes 36 may be aligned and secured together. Then, all of themembranes 36 may be manufactured simultaneously by grinding and etchingthe silicon wafer to its desired final thickness. The siliconglasssubstrate 34membrane 36 sandwich may then be divided by any suitablemeans (such as dicing) into individual chips, each chip bearing at leastone filter 380 or filter 380regulator 32 combination.

One of the advantages of using etching and anodic bonding processes tomanufacture the filter 380, and the filter 380regulator 32 combination,is that such processes enable high quality, very reliable filters 380,and filter 380regulator 32 combinations, to be mass produced in greatnumbers at a cost so low that the filters 380 and the filter380regulator 32 combinations may be considered to be disposable.

Further, it should also be noted that the filter 380 and the filter380regulator 32 combination are stunning in their simplicity since theyboth have only two basic parts, i.e. their substrates 34 and theirmembranes 36; and since the regulator 32 has only one moving part, i.e.,its flexure 28, which merely bows during operation of the filter380regulator 32 combination. In addition, because the raw materials fromwhich the filter 380 and the filter 380regulator 32 combination may bemanufactured may be very inexpensive, such as glass and silicon, thecost of the filter 380 and the filter 380regulator 32 combination mayheld to a very low level.

MICROMACHINED SLAB FILTER 400 (FIG. 44): STRUCTURE, OPERATION, THEORYAND MANUFACTURE

The micromachined slab filter 400 which is illustrated in FIG. 44 is thesame as, or at least similar to, the micromachined slab filter 340 ofFIGS. 41-43 in its structure, operation, theory and manufacture, exceptfor those differences which will be made apparent by an examination ofall of the Figures and all of the disclosures in this document.Accordingly, the respective parts of the filter 400 of FIG. 44 has beengiven the same reference numerals as the corresponding parts of thefilter 340 of FIGS. 41-43, for clarity and simplicity.

Turning again to FIG. 44, it is seen that the substrate 34 may beprovided with a filter element entrance 402, which may extend from thefilter mounting lip 382 to the edge of the substrate 34. The filterelement entrance 402 and the filter mounting lip 382 may be recessedbelow the substrate 34's top surface by about the same amount.

As a result, after the slab filter 400's substrate 34 and membrane 36are bonded together, the filter element entrance 402 and the overlayingportion of the membrane 36 form a slot through which the filter element390 may be inserted into position on the filter mounting lip 382. Afterthe filter element 390 is in place on the filter mounting lip 382, thefilter element may be bonded and sealed in place in any suitable way,such as by using a bonding and sealing process which is the same as, orat least similar to, the bonding and sealing process which was used tobond and seal the FIGS. 41-43 substrate 34, filter element 390 andmembrane 36 together, except for those differences which will be madeapparent by an examination of all of the Figures and disclosures in thisdocument.

It is understood that the foregoing forms of the invention weredescribed andor illustrated strictly by way of non-limiting example.

In view of all of the disclosures herein, these and furthermodifications, adaptations and variations of the present invention willnow be apparent to those skilled in the art to which it pertains, withinthe scope of the following claims.

What is claimed is:
 1. A micromachined fluid handling apparatuscomprising a micromachined filter, and a micromachined fluid handlingdevice; said fluid handling apparatus further comprising a substrate anda membrane mounted on said substrate; said substrate and said membranecomprising respective mounting portions secured together; wherein saidmicromachined filter and said micromachined fluid handling devicecomprise respective integral sections of said substrate and saidmembrane; wherein said micromachined filter further comprises a filterelement means for removing particles of at least a predetermined sizefrom an unfiltered fluid from an unfiltered fluid source, a first inletport means for receiving said unfiltered fluid from said unfilteredfluid source and for conveying said unfiltered fluid to said filterelement means, and a first outlet port means for conveying a filteredfluid from said filter element means and for permitting said filteredfluid to exit from said micromachined filter; and wherein saidmicromachined fluid handling device comprises an inlet port means forreceiving said filtered fluid from said first outlet port means, and anoutlet port means for permitting said filtered fluid to exit from saidmicromachined fluid handling device.
 2. The apparatus according to claim1, wherein said mounting portions are anodically bonded to each other.3. The apparatus according to claim 1, wherein at least one of saidsubstrate and said membrane comprises at least one internal exposedportion which is exposed to said fluid during operation of saidapparatus; wherein said apparatus further comprises acorrosion-resistant layer on at least part of said at least one exposedportion; and wherein said corrosion-resistant layer is anodically bondedto said at least one exposed portion.
 4. The apparatus according toclaim 3, wherein said corrosion-resistant layer comprises an oxide of atransition metal selected from the group consisting essentially oftitanium and zirconium.
 5. The apparatus according to claim 3, whereinsaid substrate and said membrane each comprise at least one freeportion; wherein said free portions of said substrate and said membraneare not anodically bonded to each other; wherein saidcorrosion-resistant layer comprises a means for serving the dualfunctions of: (a) helping to prevent corrosion of said part of said atleast one exposed portion to which said corrosion-resistant layer isanodically bonded, and (b) helping to prevent the accidental anodicbonding of said at least one free portion of said substrate to said atleast one free portion of said membrane.
 6. The apparatus according toclaim 1, wherein said filter element means comprises an array of filterslots micromachined into said substrate.
 7. The apparatus according toclaim 6, wherein said array of filter slots at least substantiallysurrounds said fluid handling device.
 8. The apparatus according toclaim 7, wherein said micromachined fluid handling device comprises aradial flow regulator; and wherein said radial flow regulator furthercomprises a regulator seat micromachined into said substrate; a membranesection of said micromachined fluid handling device comprising a flexureportion which extends over said regulator seat, wherein said flexureportion has a top surface and a bottom surface; and a regulator gaplocated between said bottom surface and said regulator seat; whereinsaid inlet port means of said micromachined fluid handling device isadapted for conveying said filtered fluid to said regulator gap; whereinsaid outlet port means of said micromachined fluid handling device isadapted for conveying said filtered fluid from said regulator gap andout of said micromachined fluid handling device; wherein duringoperation of said regulator, said top surface is exposed to saidunfiltered fluid from said unfiltered fluid source; wherein there is adriving pressure difference between said unfiltered fluid at said firstinlet port means and said filtered fluid at said outlet port means ofsaid micromachined fluid handling device; wherein said driving pressuredifference acts between said top surface and said outlet port means ofsaid micromachined fluid handling device; wherein in response to anincrease in said driving pressure difference said flexure portion bowstowards said regulator seat an increased amount, to reduce the size ofsaid regulator gap and to tend to hold a flow of said filtered fluidthrough said regulator within a predetermined fluid flow ranges, despitesaid increase in said driving pressure difference; and wherein inresponse to a decrease in said driving pressure difference, said flexureportion bows towards said regulator seat a decreased amount, to increasethe size of said regulator gap and to tend to hold said flow of saidfiltered fluid through said regulator within said predetermined fluidflow range, despite said decrease in said driving pressure difference.9. The apparatus according to claim 1, wherein said first inlet portmeans comprises an inlet cavity for distributing said unfiltered fluidto said array of filter slots; wherein said inlet cavity at leastsubstantially surrounds said array of filter slots; wherein said firstoutlet port means comprises an outlet cavity for collecting saidfiltered fluid from said array of filter slots; and wherein said outletcavity at least substantially surrounds said fluid handling device. 10.The apparatus according to claim 9, wherein said micromachined fluidhandling device comprises a radial flow regulator; and wherein saidradial flow regulator further comprises a regulator seat micromachinedinto said substrate; a membrane section of said micromachined fluidhandling device comprising a flexure portion which extends over saidregulator seat, wherein said flexure portion has a top surface and abottom surface; and a regulator gap located between said bottom surfaceand said regulator seat; wherein said inlet port means of saidmicromachined fluid handling device is adapted for conveying saidfiltered fluid to said regulator gap; wherein said outlet port means ofsaid micromachined fluid handling device is adapted for conveying saidfiltered fluid from said regulator gap and out of said micromachinedfluid handling device; wherein during operation of said regulator, saidtop surface is exposed to said unfiltered fluid from said unfilteredfluid source; wherein there is a driving pressure difference betweensaid unfiltered fluid at said first inlet port means and said filteredfluid at said outlet port means of said micromachined fluid handlingdevice; wherein said driving pressure difference acts between said topsurface an said outlet port means of said micromachined fluid handlingdevice; wherein in response to an increase in said driving pressuredifference said flexure portion bows towards said regulator seat andincreased amount, to reduce the size of said regulator gap and to tendto hold a flow of said filtered fluid through said regulator within apredetermined fluid flow range, despite said increase in said drivingpressure difference; and wherein in response to a decrease in saiddriving pressure difference, said flexure portion bows towards saidregulator seat a decreased amount, to increase the size of saidregulator gap and to tend to hold said flow of said filtered fluidthrough said regulator within said predetermine fluid flow range,despite said decrease in said driving pressure difference.
 11. Theapparatus according to claim 1, wherein said filter element meanscomprises a slab filter element; wherein said first inlet port meanscomprises an inlet port in said membrane; wherein said first outlet portmeans comprises an outlet cavity in said substrate; and wherein, duringoperation of said filter, said unfiltered fluid flows from saidmembrane's inlet port to said slab filter element, and wherein saidfiltered fluid flows from said slab filter element to said substrate'soutlet cavity.
 12. The apparatus according to claim 11, wherein saidmicromachined fluid handling device comprises a radial flow regulator;and wherein said radial flow regulator further comprises a regulatorseat micromachined into said substrate; a membrane section of saidmicromachined fluid handling device comprising a flexure portion whichextends over said regulator seat, wherein said flexure portion has a topsurface and a bottom surface; and a regulator gap located between saidbottom surface and said regulator seat; wherein said inlet port means ofsaid micromachined fluid handling device is adapted for conveying saidfiltered fluid to said regulator gap; wherein said outlet port means ofsaid micromachined fluid handling device is adapted for conveying saidfiltered fluid from said regulator gap and out of said micromachinedfluid handling device; wherein during operation of said regulator, saidtop surface is exposed to said unfiltered fluid from said unfilteredfluid source; wherein there is a driving pressure difference betweensaid unfiltered fluid at said first inlet port means and said filteredfluid at said outlet port means of said micromachined fluid handlingdevice; wherein said driving pressure difference acts between said topsurface and said outlet port means of said micromachined fluid handlingdevice; wherein in response to an increase in said driving pressuredifference said flexure portion bows towards said regulator seat anincreased amount, to reduce the size of said regulator gap and to tendto hold a flow of said filtered fluid through said regulator within apredetermined fluid flow range, despite said increase in said drivingpressure difference; and wherein in response to a decrease in saiddriving pressure difference, said flexure portion bows towards saidregulator seat a decreased amount, to increase the size of saidregulator gap and to tend to hold said flow of said filtered fluidthrough said regulator within said predetermined fluid flow range,despite said decrease in said driving pressure difference.
 13. Theapparatus according to claim 11, wherein said filter element is locatedbetween said membrane's inlet port and said substrate's outlet cavity.14. The apparatus according to claim 11, wherein said filter furthercomprises a filter element entrance means for permitting said filterelement to be inserted between said membrane's inlet port and saidsubstrate's outlet cavity.
 15. The apparatus according to claim 11,wherein said filter element comprises an exposed filter element areawhich is exposed to said unfiltered fluid; wherein said membrane's inletport has an area which is at least about equal to said exposed filterelement area; and wherein said substrate's outlet cavity has an areawhich is at least about equal to said exposed filter element area. 16.The apparatus according to claim 1, wherein said filter element meanscomprises a slab filter element; wherein said first inlet port means ofsaid micromachined filter comprises a surface of said slab filterelement which is exposed to said unfiltered fluid during use of saidmicromachined filter; wherein said first outlet port means of saidmicromachined filter comprisesoutlet port in said membrane and an outletcavity in said substrate; wherein said membrane is located between saidfilter element means and said substrate; and wherein, during operationof said micromachined filter, said filtered fluid flows sequentiallythrough said membrane's outlet port and said substrate's outlet cavity.